

A093678


Sequence contains no 3term arithmetic progression, starting with 1,7.


9



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
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OFFSET

1,2


COMMENTS

a(1)=1, a(2)=7; 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..57.
Index entries related to nonaveraging sequences


FORMULA

a(n) = sum[k=1, n1, (3^A007814(k)+1)/2] + f(n), with f(n) an 8periodic function with values {1, 6, 5, 6, 2, 6, 5, 7, ...}, as proved by Lawrence Sze.


CROSSREFS

Cf. A004793, A033157, A093679A093681, A092482.
Row 3 of array in A093682.
Sequence in context: A096677 A120192 A256651 * A188052 A266727 A214004
Adjacent sequences: A093675 A093676 A093677 * A093679 A093680 A093681


KEYWORD

nonn


AUTHOR

Ralf Stephan, Apr 09 2004


STATUS

approved



