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A083096 Numbers n such that 3 divides sum(k=1,n, C(2k,k) ). 8
0, 12, 30, 36, 84, 90, 108, 120, 246, 252, 270, 282, 324, 336, 354, 360, 732, 738, 756, 768, 810, 822, 840, 846, 972, 984, 1002, 1008, 1056, 1062, 1080, 1092, 2190, 2196, 2214, 2226, 2268, 2280, 2298, 2304, 2430, 2442, 2460, 2466, 2514, 2520, 2538, 2550 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Apparently a(n)/3 (mod 3) = A010060(n), the Thue-Morse sequence

LINKS

Table of n, a(n) for n=1..48.

FORMULA

It appears that sequence gives n such that the coefficient of x^n equals 1 in prod (k>=1, 1-x^(3^k))

MATHEMATICA

Reap[ For[n = 0, n <= 3000, n = n + 3, If[ Divisible[ Sum[ Binomial[2 k, k], {k, 1, n}], 3], Print[n]; Sow[n]]]][[2, 1]] (* Jean-Fran├žois Alcover, Jul 01 2013 *)

CROSSREFS

Cf. A066796, A083097, A081601.

Sequence in context: A050689 A144565 A115912 * A289691 A145469 A024364

Adjacent sequences:  A083093 A083094 A083095 * A083097 A083098 A083099

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, Apr 22 2003

STATUS

approved

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Last modified February 23 23:56 EST 2018. Contains 299595 sequences. (Running on oeis4.)