

A093680


Sequence contains no 3term arithmetic progression, starting with 1,19.


6



1, 19, 20, 22, 23, 28, 29, 31, 32, 46, 47, 49, 50, 56, 58, 59, 82, 100, 101, 103, 104, 109, 110, 112, 113, 127, 128, 130, 131, 137, 139, 140, 244, 262, 263, 265, 266, 271, 272, 274, 275, 289, 290, 292, 293, 299, 301, 302, 325, 343, 344, 346, 347, 352, 353
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OFFSET

1,2


COMMENTS

a(1)=1, a(2)=19; 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, 18, 17, 18, 14, 18, 17, 19, 5, 18, 17, 18, 14, 19, 19, 19, ...}, as proved by Lawrence Sze.


CROSSREFS

Cf. A004793, A033157, A093678A093681, A092482.
Row 5 of array in A093682.
Sequence in context: A004508 A018824 A289469 * A007640 A265201 A274340
Adjacent sequences: A093677 A093678 A093679 * A093681 A093682 A093683


KEYWORD

nonn


AUTHOR

Ralf Stephan, Apr 09 2004


STATUS

approved



