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Search: id:A108279
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| A108279 |
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a(n) = number of squares with corners on an n X n grid, distinct up to congruence. |
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+0
3
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| 0, 1, 3, 5, 8, 11, 15, 18, 23, 28, 33, 38, 45, 51, 58, 65, 73, 80, 89, 97, 107, 116, 126, 134, 146, 158, 169, 180, 192, 204, 218, 228, 243, 257, 270, 285, 302, 316, 331, 346, 364, 379, 397, 414, 433, 451, 468, 484, 505, 523, 544, 563, 584, 603, 625
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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Number of different sizes occurring among the A002415(n)=n^2*(n^2-1)/12 squares that can be drawn using points of an n X n square array as corners.
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LINKS
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H. Bottomley, Illustration of initial terms of A002415
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EXAMPLE
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a(3)=3 because the 6 different squares that can be drawn on a 3 X 3 square lattice come in 3 sizes:
4 squares of side length 1:
x.x.o....o.x.x....o.o.o....o.o.o
x.x.o....o.x.x....x.x.o....o.x.x
o.o.o....o.o.o....x.x.o....o.x.x
1 square of side length sqrt(2):
o.x.o
x.o.x
o.x.o
1 square of side length 2:
x.o.x
o.o.o
x.o.x
a(4)=5 because there are 5 different sizes of squares that can be drawn using the points of a 4 X 4 square lattice:
x.x.o.o....o.x.o.o....x.o.x.o....o.x.o.o....x.o.o.x
x.x.o.o....x.o.x.o....o.o.o.o....o.o.o.x....o.o.o.o
o.o.o.o....o.x.o.o....x.o.x.o....x.o.o.o....o.o.o.o
o.o.o.o....o.o.o.o....o.o.o.o....o.o.x.o....x.o.o.x
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CROSSREFS
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Cf. A002415 = 4-dimensional pyramidal numbers, A024206.
Sequence in context: A022433 A081401 A003311 this_sequence A002821 A046992 A001463
Adjacent sequences: A108276 A108277 A108278 this_sequence A108280 A108281 A108282
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KEYWORD
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nonn
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AUTHOR
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Hugo Pfoertner (hugo(AT)pfoertner.org), Jun 05 2005
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EXTENSIONS
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More terms from David W. Wilson, Jun 07 2005
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