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 A247502 #14 Nov 11 2024 03:57:28 %S A247502 1,1,1,1,4,1,1,13,9,1,1,41,57,16,1,1,131,320,165,25,1,1,428,1711,1420, %T A247502 380,36,1,1,1429,8967,11151,4620,756,49,1,1,4861,46663,83202,49665, %U A247502 12306,1358,64,1,1,16795,242634,602407,495327,172893,28476,2262,81,1 %N A247502 Triangle read by rows: coefficients of polynomials related to the exponential generating function of sequences generated by Narayana polynomials evaluated at the integers; n>=1, 0<=k<n. %C A247502 Definition: Let N(n,x) = Sum_{j=0..n-1} x^j*C(n,j)^2*(n-j)/(n*(j+1)) for n>0 and N(0,x) = 1, further let p(n,x) be implicitly defined by N(n,k) = k!*[x^k](exp(x)*p(n,x)), then T(n,k) = [x^k] p(n,x). %F A247502 T(n, 0) = T(n, n-1) = 1. %F A247502 T(n, 1) = A001453(n) = A000108(n) - 1 for n>=2. %F A247502 T(n, n-2) = (n-1)^2 for n>=2. %e A247502 Triangle T(n,k) begins: %e A247502 [n\k][0, 1, 2, 3, 4, 5, 6, 8, 9] %e A247502 [1] 1, %e A247502 [2] 1, 1, %e A247502 [3] 1, 4, 1, %e A247502 [4] 1, 13, 9, 1, %e A247502 [5] 1, 41, 57, 16, 1, %e A247502 [6] 1, 131, 320, 165, 25, 1, %e A247502 [7] 1, 428, 1711, 1420, 380, 36, 1, %e A247502 [8] 1, 1429, 8967, 11151, 4620, 756, 49, 1, %e A247502 [9] 1, 4861, 46663, 83202, 49665, 12306, 1358, 64, 1. %e A247502 . %e A247502 The sequence N(7,k) = 1 + 21*k + 105*k^2 + 175*k^3 + 105*k^4 + 21*k^5 + k^6 = 1, 429, 4279, 20071, 65445, ... = A090200(k) has the exponential generating function exp(x)*(1 + 428*x + 1711*x^2 + 1420*x^3 + 380*x^4 + 36*x^5 + x^6). Thus T(7,3) = 1420. %Y A247502 Cf. A243631 and the crossreferences given there. %K A247502 nonn,tabl %O A247502 1,5 %A A247502 _Peter Luschny_, Nov 18 2014