A093681 Sequence contains no 3-term arithmetic progression, starting with 1, 28.

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

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

Table of n, a(n) for n=1..55.

Index entries related to non-averaging sequences

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, A093679, A093680, A092482.

Row 6 of array in A093682.

Sequence in context: A219914 A165849 A364041 * A044874 A022398 A042580

Adjacent sequences: A093678 A093679 A093680 * A093682 A093683 A093684

Keyword

nonn

Author

Ralf Stephan, Apr 09 2004

Status

approved