OFFSET
1,1
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..2014
MATHEMATICA
Select[Range@ 300, GCD @@ Array[Function[k, Binomial[2 #, 2 k]], {# - 1}] == 2 # - 1 &] (* Michael De Vlieger, Dec 11 2015 *)
PROG
(PARI) isok(n) = (n>1) && gcd(vector(n-1, k, binomial(2*n, 2*k))) == 2*n-1; \\ Michel Marcus, Dec 08 2015, edited by Antti Karttunen, Dec 11 2015 (see A265388 for why).
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Dec 08 2015
STATUS
approved