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Search: id:A093681
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| A093681 |
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Sequence contains no 3-term arithmetic progression, starting with 1,28. |
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+0
5
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| 1, 28, 29, 31, 32, 37, 38, 40, 41, 56, 58, 59, 64, 65, 67, 68, 82, 109, 110, 112, 113, 118, 119, 121, 122, 137, 139, 140, 145, 146, 148, 149, 244, 271, 272, 274, 275, 280, 281, 283, 284, 299, 301, 302, 307, 308, 310, 311, 325, 352, 353, 355, 356, 361, 362
(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)=28; 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) a 16-periodic function with values {1, 27, 26, 27, 23, 27, 26, 27, 14, 28, 28, 28, 28, 28, 28, 28, ...}, n>=1 (conjectured and checked up to n=1000).
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CROSSREFS
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Cf. A004793, A033157, A093678-A093681, A092482.
Row 6 of array in A093682.
Sequence in context: A040757 A022362 A165849 this_sequence A044874 A022398 A042580
Adjacent sequences: A093678 A093679 A093680 this_sequence A093682 A093683 A093684
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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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