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Search: id:A093678
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| A093678 |
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Sequence contains no 3-term arithmetic progression, starting with 1,7. |
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+0
5
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| 1, 7, 8, 10, 11, 16, 17, 20, 28, 34, 35, 37, 38, 43, 44, 47, 82, 88, 89, 91, 92, 97, 98, 101, 109, 115, 116, 118, 119, 124, 125, 128, 244, 250, 251, 253, 254, 259, 260, 263, 271, 277, 278, 280, 281, 286, 287, 290, 325, 331, 332, 334, 335, 340, 341, 344, 352
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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a(1)=1, a(2)=7; a(n) is least k such that no three terms of a(1),a(2),...,a(n-1),k form an arithmetic progression.
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FORMULA
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a(n) = sum[k=1, n-1, (3^A007814(k)+1)/2] + f(n), with f(n) an 8-periodic function with values {1, 6, 5, 6, 2, 6, 5, 7, ...}, as proved by Lawrence Sze.
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CROSSREFS
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Cf. A004793, A033157, A093679-A093681, A092482.
Row 3 of array in A093682.
Sequence in context: A105860 A096677 A120192 this_sequence A037263 A125134 A120175
Adjacent sequences: A093675 A093676 A093677 this_sequence A093679 A093680 A093681
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KEYWORD
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nonn
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AUTHOR
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Ralf Stephan (ralf(AT)ark.in-berlin.de), Apr 09 2004
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