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 A361834 #15 Mar 26 2023 11:14:46 %S A361834 1,1,2,1,2,6,1,2,4,20,1,2,2,8,70,1,2,0,-2,16,252,1,2,-2,-10,-14,32, %T A361834 924,1,2,-4,-16,-22,-32,64,3432,1,2,-6,-20,-10,12,-30,128,12870,1,2, %U A361834 -8,-22,20,118,174,64,256,48620,1,2,-10,-22,66,242,304,344,346,512,184756 %N A361834 Square array T(n,k), n >= 0, k >= 0, read by antidiagonals downwards, where T(n,k) = Sum_{j=0..n} (-1)^(n-j) * binomial(2*j,j) * binomial(k*j,n-j). %F A361834 G.f. of column k: 1/sqrt(1 - 4*x*(1-x)^k). %F A361834 n*T(n,k) = 2 * Sum_{j=0..k} (-1)^j * binomial(k,j)*(2*n-1-j)*T(n-1-j,k) for n > k. %e A361834 Square array begins: %e A361834 1, 1, 1, 1, 1, 1, 1, ... %e A361834 2, 2, 2, 2, 2, 2, 2, ... %e A361834 6, 4, 2, 0, -2, -4, -6, ... %e A361834 20, 8, -2, -10, -16, -20, -22, ... %e A361834 70, 16, -14, -22, -10, 20, 66, ... %e A361834 252, 32, -32, 12, 118, 242, 342, ... %e A361834 924, 64, -30, 174, 304, 82, -678, ... %o A361834 (PARI) T(n, k) = sum(j=0, n, (-1)^(n-j)*binomial(2*j, j)*binomial(k*j, n-j)); %Y A361834 Columns k=0..4 give A000984, A000079, A361815, A361816, A361817. %Y A361834 Main diagonal gives A361835. %Y A361834 Cf. A361830. %K A361834 sign,tabl %O A361834 0,3 %A A361834 _Seiichi Manyama_, Mar 26 2023