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Search: id:A145199
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| A145199 |
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Not squarefree numbers n such that n+1 is prime. |
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+0
1
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| 4, 12, 16, 18, 28, 36, 40, 52, 60, 72, 88, 96, 100, 108, 112, 126, 136, 148, 150, 156, 162, 172, 180, 192, 196, 198, 228, 232, 240, 250, 256, 268, 270, 276, 280, 292, 306, 312, 316, 336, 348, 352, 372, 378, 388, 396, 400, 408, 420, 432, 448, 456, 460, 486, 490
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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4 is in the sequence because it is not squarefree and 5 is prime. [From Emeric Deutsch (deutsch(AT)duke.poly.edu), Oct 12 2008]
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MAPLE
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Contribution from Emeric Deutsch (deutsch(AT)duke.poly.edu), Oct 12 2008: (Start)
with(numtheory): a:=proc(n) if issqrfree(n)=false and isprime(n+1)=true then n else end if end proc: seq(a(n), n=1..600);
with(numtheory): a:=proc(k) if issqrfree(ithprime(k)-1)=false then ithprime(k)-1 else end if end proc: seq(a(k), k=1..110); (End)
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MATHEMATICA
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Select[Prime[Range[120]]-1, !SquareFreeQ[ # ]&] [From T. D. Noe (noe(AT)sspectra.com), Oct 06 2008]
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CROSSREFS
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Cf. A006093.
Cf. A013929, A077064.
Sequence in context: A144976 A119622 A067575 this_sequence A082420 A053362 A077770
Adjacent sequences: A145196 A145197 A145198 this_sequence A145200 A145201 A145202
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KEYWORD
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easy,nonn
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AUTHOR
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Giovanni Teofilatto (g.teofilatto(AT)tiscalinet.it), Oct 04 2008
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EXTENSIONS
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Corrected and extended by T. D. Noe (noe(AT)sspectra.com), Emeric Deutsch (deutsch(AT)duke.poly.edu) and R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 05 2008
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