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 A103731 #4 Jun 16 2016 23:27:27 %S A103731 1,13,191,457,1713,2899,6997,19769,26521,57313,89161,109327,159713, %T A103731 265617,417079,479641,709963,903981,1014697,1408369,1727987,2305689, %U A103731 3287713,3882401,4208317,4921263,5309929,6155857,9930313,11272171 %N A103731 Column k=4 sequence of array A103728. %C A103731 The two a(n) formulas, given below, produce natural numbers for all n>=0. %F A103731 a(n)=A103728(n+3, 4)=(1 +(p(n+3)-1)*binomial(p(n+3)-1, 4))/p(n+3), with p(n):=A000040(n) (n-th prime). %F A103731 a(n)= (74 - 85*p(n+3) + 45*p(n+3)^2 - 11*p(n+3)^3 + p(n+3)^4)/4! = sum(A103718(k, m)*p(n+3)^m, m=0..4)/4!. %K A103731 nonn,easy %O A103731 0,2 %A A103731 _Wolfdieter Lang_, Feb 24 2005