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 A265394 #15 Jul 19 2022 13:24:31
%S A265394 1,2,3,6,7,15,19,31,37,79,97,139,157,199,211,229,271,307,331,337,367,
%T A265394 379,439,499,547,577,601,607,619,661,691,727,811,829,877,937,967,997,
%U A265394 1009,1069,1171,1237,1279,1297,1399,1429,1459,1531,1609,1627,1657,1759,1867,2011,2029,2089,2131,2137,2179,2221,2281,2311
%N A265394 Positions of records in A265388.
%C A265394 Question: Apart from a(1)=1, a(4)=6 and a(6)=15, are all other terms primes? See also comments in A265395 & A265396.
%H A265394 Antti Karttunen, <a href="/A265394/b265394.txt">Table of n, a(n) for n = 1..192</a>
%t A265394 DeleteDuplicates[Table[{n,GCD@@Array[Binomial[2 n,2 #]&,{n-1}]},{n,2350}],GreaterEqual[ #1[[2]],#2[[2]]]&][[All,1]] (* _Harvey P. Dale_, Jul 19 2022 *)
%o A265394 (PARI) lista(nn) = {r = 0; for (n=1, nn, nr = gcd(vector(n-1, k, binomial(2*n, 2*k))); if (nr > r, print1(n, ", "); r = nr););} \\ _Michel Marcus_, Dec 08 2015
%Y A265394 Cf. A265388.
%Y A265394 Cf. A265395 (gives the record values), A265396.
%K A265394 nonn
%O A265394 1,2
%A A265394 _Antti Karttunen_, Dec 08 2015