1,2

It is understood that a(n) is taken to be the smallest number >= a(n-1) which is compatible with the description.

Also called Silverman's sequence.

Vardi gives several identities satisfied by A001463 and this sequence.

We can interpret A001462 as a triangle: start with 1; 2,2; 3,3; and proceed by letting the row sum of row m-1 be the number of elements of row m. The partial sums of the row sums give 1, 5, 11, 38, 272, ... Conjecture: this proceeds as Lionel Levile's sequence A014644. See also A113676. - Floor van Lamoen, fvlamoen(AT)hotmail.com, Nov 06 2005.

The g.f. -z*(-1+z**4+z**7-z**8+z**9-z**3-z-z**11+z**12)/(1+z)/(z**2+1)/(z-1)**2 conjectured by S. Plouffe in his 1992 dissertationd is wrong. - N. J. A. Sloane (njas(AT)research.att.com), May 13 2008

N. J. A. Sloane, Seven Staggering Sequences, in Homage to a Pied Puzzler, E. Pegg Jr., A. H. Schoen and T. Rodgers (editors), A. K. Peters, Wellesley, MA, 2009, pp. 93-110.

G. Everest, A. van der Poorten, I. Shparlinski and T. Ward, Recurrence Sequences, Amer. Math. Soc., 2003; p. 10.

S. W. Golomb, Problem 5407, Amer. Math. Monthly, 73 (1966), 674.

R. L. Graham, D. E. Knuth and O. Patashnik, Concrete Mathematics. Addison-Wesley, Reading, MA, 1990, p. 66.

J. Grytczuk, Another variation on Conway's recursive sequence, Discr. Math. 282 (2004), 149-161.

R. K. Guy, Unsolved Problems in Number Theory, E25.

D. Marcus and N. J. Fine, Solutions to Problem 5407, Amer. Math. Monthly 74 (1967), 740-743.

Petermann, Y.-F. S., On Golomb's self-describing sequence, J. Number Theory 53 (1995), 13-24.

Petermann, Y.-F. S., On Golomb's self-describing sequence, II, Arch. Math. (Basel) 67 (1996), 473-477.

Petermann, Y.-F. S., Is the error term wild enough? Analysis (Munich) 18 (1998), 245-256.

Petermann, Y.-F. S. and Remy, Jean-Luc, Golomb's self-described sequence and functional-differential equations, Illinois J. Math. 42 (1998), 420-440.

J. L. Remy, J. Number Theory, 66 (1997), 1-28.

J. Sauerberg and L. Shu, The long and the short on counting sequences, Amer. Math. Monthly, 104 (1997), 306-317.

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

I. Vardi, The error term in Golomb's sequence, J. Number Theory, 40 (1992), 1-11. (See also the Math. Review, 93d:11103)

T. D. Noe, Table of n, a(n) for n = 1..10000

B. Cloitre, N. J. A. Sloane and M. J. Vandermast, Numerical analogues of Aronson's sequence, J. Integer Seqs., Vol. 6 (2003), #03.2.2.

B. Cloitre, N. J. A. Sloane and M. J. Vandermast, Numerical analogues of Aronson's sequence (math.NT/0305308)

Y.-F. S. Petermann, J.-L. Remy and I. Vardi, Discrete derivatives of sequences, Adv. in Appl. Math. 27 (2001), 562-84.

S. Plouffe, Approximations de S\'{e}ries G\'{e}n\'{e}ratrices et Quelques Conjectures, Dissertation, Universit\'{e} du Qu\'{e}bec \`{a} Montr\'{e}al, 1992.

S. Plouffe, 1031 Generating Functions and Conjectures, Universit\'{e} du Qu\'{e}bec \`{a} Montr\'{e}al, 1992.

N. J. A. Sloane, My favorite integer sequences, in Sequences and their Applications (Proceedings of SETA '98).

N. J. A. Sloane, Seven Staggering Sequences.

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

Index entries for "core" sequences

Index entries for sequences of the a(a(n)) = 2n family

a(n) = phi^(2-phi)*n^(phi-1) + E(n), where phi is the golden number (1+sqrt(5))/2 (Marcus and Fine) and E(n) is an error term which Vardi shows is O( n^(phi-1) / log n ).

a(1) = 1; a(n+1) = 1 + a(n+1-a(a(n))). - C. L. Mallows.

a(1)=1, a(2)=2 and for a(1)+a(2)+..+a(n-1) < k <= a(1)+a(2)+...+a(n) we have a(k)=n - Benoit Cloitre (benoit7848c(AT)orange.fr), Oct 07 2003

G.f.: Sum_{k>0} x^a(k). - Michael Somos Oct 21 2006

a(1) = 1, so 1 only appears once. The next term is therefore 2, which means 2 appears twice and so a(3) is also 2 but a(4) must be 3. And so on.

t1 := [ 1, 2, 2 ]: for i from 3 to 20 do t2 := t1; for j from 1 to t1[ i ] do t2 := [ op(t2), i ]; od: t1 := t2; od: t1; A001462 := n->t1[n];

a[1] = 1; a[n_] := a[n] = 1 + a[n - a[a[n - 1]]]; Table[ a[n], {n, 84}] (from Robert G. Wilson v (rgwv(at)rgwv.com), Aug 26 2005)

(PARI) a=[ 1, 2, 2 ]; for(n=3, 20, for(i=1, a[ n ], a=concat(a, n))); a

(PARI) {a(n)=local(A, t, i); if(n<3, max(0, n), A=vector(n); t=A[i=2]=2; for(k=3, n, A[k]=A[k-1]+if(t--==0, t=A[i++ ]; 1)); A[n])} /* Michael Somos Oct 21 2006 */

(MAGMA) [ n eq 1 select 1 else 1+Self(n-Self(Self(n-1))) : n in [1..100] ]; - from Sergei Haller (sergei(AT)sergei-haller.de), Dec 21 2006

Cf. A000002, A001463 (partial sums).

Adjacent sequences: A001459 A001460 A001461 this_sequence A001463 A001464 A001465

Sequence in context: A126848 A067085 A055086 this_sequence A082462 A005041 A030530

easy,nonn,nice,core

N. J. A. Sloane (njas(AT)research.att.com).