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 A266366 #8 Feb 03 2016 11:48:51 %S A266366 2,3,12,10,3160 %N A266366 Least k such that prime(n) is the smallest odd prime factor of C(2k,k). %C A266366 If n>0, then a(n+2) >= A129489(n) = least k>1 such that binomial(2k,k) is not divisible by any of the first n odd primes. %C A266366 It is not known whether any more terms exist. See A129489 for bounds, comments and references. %e A266366 C(2,1) = 2, C(4,2) = 6 = 2 * 3, C(6,3) = 20 = 2^2 * 5, and 3 = prime(2), 5 = prime(3), so a(2) = 2 and a(3) = 3. %o A266366 (PARI) valp(n, p)=my(s); while(n\=p, s+=n); s %o A266366 a(n)=my(q=prime(n),k=1); while(k++, forprime(p=3,q-1, if(valp(2*k, p)>2*valp(k, p), next(2))); if(valp(2*k, q)>2*valp(k, q), return(k))) \\ _Charles R Greathouse IV_, Feb 03 2016 %Y A266366 Cf. A000984, A129488, A129489, A030979. %K A266366 bref,hard,more,nonn %O A266366 2,1 %A A266366 _Jonathan Sondow_, Jan 18 2016