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Search: id:A160426
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| A160426 |
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Toothpick sequence starting from an asymmetric cross, with four edges of length 1, 2, 3 and 4, formed by five toothpicks of length 2. |
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+0
9
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| 0, 5, 9, 17, 30, 42, 52, 69, 90, 102, 112, 129, 150, 170
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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On the infinite square grid we start at stage 0 with no toothpicks. At stage 1 we place three consecutive toothpicks and two orthogonal toothpicks, as an asymetric cross with four edges of length 1, 2, 3, and 4, then a(1)=5. At stage 2 we place 4 toothpicks. And so on...
The sequence gives the number of toothpicks in the sieve after n stages. A160427 (the first differences) gives the number added at the nth stage. See A139250 for more information about toothpick sequences.
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CROSSREFS
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Cf. A139250, A139251, A160740, A160800, A160802, A160808.
Sequence in context: A100449 A146284 A081295 this_sequence A059743 A000322 A020737
Adjacent sequences: A160423 A160424 A160425 this_sequence A160427 A160428 A160429
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KEYWORD
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more,nonn
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AUTHOR
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Omar E. Pol (info(AT)polprimos.com), May 25 2009, May 29 2009
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