A140973 Numbers n such that arithmetic mean of squares of the first n tribonacci numbers is an integer.

1, 2, 8, 15, 16, 18, 22, 32, 47, 48, 53, 58, 64, 70, 77, 78, 80, 94, 95, 96, 103, 106, 128, 138, 163, 199, 206, 256, 257, 266, 269, 311, 326, 330, 352, 358, 385, 397, 398, 401, 419, 421, 499, 512, 514, 538, 587, 599, 617, 622, 640, 672, 683, 757, 768, 770, 773

Offset

1,2

Comments

Could arithmetic tribonacci mean (T(0)+...+T(n-1)) / n be an integer?

The arithmetic means are integers for the first 1, 2, 47, 53, 94, 103, 106 etc. tribonacci numbers. - R. J. Mathar, Aug 04 2008

Links

Table of n, a(n) for n=1..57.

Formula

n such that (T(0)^2+ T(1)^2+ ... + T(n-1)^2) / n is an integer. T(i) = i-th tribonacci number.

Crossrefs

Cf. A000073.

Cf. A107239. - R. J. Mathar, Aug 04 2008

Sequence in context: A054981 A059449 A272930 * A065907 A031272 A277139

Adjacent sequences: A140970 A140971 A140972 * A140974 A140975 A140976

Keyword

easy,nonn

Author

Ctibor O. Zizka, Jul 27 2008

Extensions

Added 1 and 2 and extended from 32 on, R. J. Mathar, Aug 04 2008

Status

approved