OFFSET
1,1
COMMENTS
Contains no primes or prime powers. - Robert Israel, Dec 10 2015
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..6571
MAPLE
select(n -> igcd(seq(binomial(2*n, 2*k), k=1..n-1)) = 1, [$1..200]); # Robert Israel, Dec 10 2015
MATHEMATICA
Select[Range@ 200, GCD @@ Table[Binomial[2 #, 2 k], {k, # - 1}] == 1 &] (* Michael De Vlieger, Dec 09 2015, modified to match the new corrected definition by Antti Karttunen, Dec 11 2015 *)
PROG
(PARI) isok(n) = (n>1) && gcd(vector(n-1, k, binomial(2*n, 2*k))) == 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