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 A226891 #11 Jun 21 2013 17:33:36 %S A226891 1,2,4,19,63,153,1273,2090,19227,266133,868868,10631543,264365332, %T A226891 662822809,129102309125 %N A226891 Least k such that k(k+1)(k+2)(k+3) is divisible by prime(n)#. %C A226891 Essentially indices of records in A053672. %F A226891 Let p be the n-th prime, then (4p#)^(1/4) - 2 < a(n) < p#; in particular, a(n) >> exp(p/4). %e A226891 63 is in the sequence because {63, 64, 65, 66} are divisible by 2, 3, 5, 7, 11, and 13; no smaller number is divisible by all of these primes. %o A226891 (PARI) a(n)=if(n<3,return(1));my(p=prime(n),P=prod(i=1,n-1,prime(i))/6, t=sqrtnint(24*p^2*P,4)+1); forstep(k=max(t\p,1)*p-3,P+2,[1,1,1,p-3], if(gcd(P, (k+3)*(k+2)*(k^2+k))==P,return(k))) %Y A226891 Cf. A053672, A078638, A002110. %K A226891 nonn,more %O A226891 2,2 %A A226891 _Charles R Greathouse IV_, Jun 20 2013 %E A226891 a(16) from _Charles R Greathouse IV_, Jun 21 2013