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A056640
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At stage 1, start with a unit square. At each successive stage add 4*(n-1) new squares around outside with edge-to-edge contacts. Sequence gives number of squares (regardless of size) at n-th stage.
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2
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1, 5, 18, 42, 83, 143, 228, 340, 485, 665, 886, 1150, 1463, 1827, 2248
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Number of unit squares at n-th stage = n^2 + (n-1)^2, A001844.
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REFERENCES
| Anthony Gardiner, "Mathematical Puzzling," Dover Publications, Inc., Mineola, NY., 1987, page 88.
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FORMULA
| G.f.: x(5x^2+2x+1)/[(1-x^2)(1-x)^3].
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CROSSREFS
| Sequence in context: A031428 A007742 A000338 * A160969 A101105 A037140
Adjacent sequences: A056637 A056638 A056639 * A056641 A056642 A056643
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KEYWORD
| nonn
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 21 2000
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