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 A093681 Sequence contains no 3-term arithmetic progression, starting with 1,28. 10
 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; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS 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. LINKS FORMULA 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). CROSSREFS Cf. A004793, A033157, A093678-A093681, A092482. Row 6 of array in A093682. Sequence in context: A022362 A219914 A165849 * A044874 A022398 A042580 Adjacent sequences:  A093678 A093679 A093680 * A093682 A093683 A093684 KEYWORD nonn AUTHOR Ralf Stephan, Apr 09 2004 STATUS approved

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Last modified June 2 14:21 EDT 2020. Contains 334787 sequences. (Running on oeis4.)