This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A265401 #24 Dec 11 2015 19:47:29
%S A265401 20,26,33,35,38,39,44,46,48,50,56,58,60,62,68,72,74,77,78,80,86,88,92,
%T A265401 93,94,95,98,102,104,105,108,110,111,116,118,119,124,130,133,134,138,
%U A265401 140,143,144,146,148,150,152,155,158,160,161,164,165,168,170,171,176,178,182,183,185,186,188,189,194,198,200
%N A265401 Numbers n for which gcd{k=1..n-1} binomial(2*n, 2*k) = 1.
%C A265401 Contains no primes or prime powers. - _Robert Israel_, Dec 10 2015
%H A265401 Antti Karttunen, <a href="/A265401/b265401.txt">Table of n, a(n) for n = 1..6571</a>
%p A265401 select(n -> igcd(seq(binomial(2*n, 2*k), k=1..n-1)) = 1, [$1..200]); # _Robert Israel_, Dec 10 2015
%t A265401 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 *)
%o A265401 (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).
%Y A265401 Cf. A265388.
%K A265401 nonn
%O A265401 1,1
%A A265401 _Antti Karttunen_, Dec 08 2015