OFFSET
1,1
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..1650
R. R. Aidagulov, M. A. Alekseyev. On p-adic approximation of sums of binomial coefficients. Journal of Mathematical Sciences 233:5 (2018), 626-634. doi:10.1007/s10958-018-3948-0 arXiv:1602.02632
M. Kontsevich, R. Stanley, O. Gorodetsky, et al. A congruence involving binomial coefficients, Mathoverflow, 2015.
FORMULA
MATHEMATICA
a[n_] := 3/n^3 DivisorSum[n, (-1)^(n+#) MoebiusMu[n/#] Binomial[2#, #]&]; Array[a, 40] (* Jean-François Alcover, Dec 18 2015 *)
PROG
(PARI) { a(n) = sumdiv(n, d, (-1)^(n+d)*moebius(n/d)*binomial(2*d, d))*3/n^3 }
CROSSREFS
KEYWORD
nonn
AUTHOR
Max Alekseyev, Feb 01 2015
STATUS
approved