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Search: id:A123663
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| A123663 |
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Number of shared edges in a spiral of n unit squares. |
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+0
1
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| 0, 1, 2, 4, 5, 7, 8, 10, 12, 13, 15, 17, 18, 20, 22, 24, 25, 27, 29, 31, 32, 34, 36, 38, 40, 41, 43, 45, 47, 49, 50, 52, 54, 56, 58, 60, 61, 63, 65, 67, 69, 71, 72, 74, 76, 78, 80, 82, 84, 85, 87, 89, 91, 93, 95, 97, 98, 100, 102, 104, 106, 108, 110, 112, 113, 115, 117, 119
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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If one constructs a square (square 1) and then draws another square of identical size beside it (square 2), the squares share 1 edge. If one then places an identical square above square 2 (instead of continuing in a straight path), there are now 2 shared edges. Continuing this pattern in an outward spiral, one finds that the number of shared edges is 4, 5, 7, ...
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MATHEMATICA
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FoldList[Plus, 0, t = Table[2, {72}]; t[[ Table[ Ceiling[n/2] Floor[n/2], {n, 2, 16}] ]]--; t] (* Robert G. Wilson v *)
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CROSSREFS
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Cf. A002620.
Adjacent sequences: A123660 A123661 A123662 this_sequence A123664 A123665 A123666
Sequence in context: A139449 A020914 A047496 this_sequence A014248 A091627 A027902
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KEYWORD
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easy,nonn
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AUTHOR
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Zacariaz Martinez (euneirophrenia(AT)gmail.com), Nov 15 2006
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EXTENSIONS
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Extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 19 2007
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