

A093681


Sequence contains no 3term 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
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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(n1),k form an arithmetic progression.


LINKS

Table of n, a(n) for n=1..55.
Index entries related to nonaveraging sequences


FORMULA

a(n) = sum[k=1, n1, (3^A007814(k)+1)/2] + f(n), with f(n) a 16periodic 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, A093678A093681, 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



