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 A318105 #20 Nov 09 2018 10:52:16 %S A318105 1,24,1,2520,120,1,369600,22680,360,1,63063000,4804800,113400,840,1, %T A318105 11732745024,1072071000,33633600,415800,1680,1,2308743493056, %U A318105 246387645504,9648639000,168168000,1247400,3024,1,472518347558400,57718587326400,2710264100544,61108047000,672672000,3243240,5040,1 %N A318105 Triangle read by rows: T(n,k) = (4*n - 3*k)!/((n-k)!^4*k!). %C A318105 Diagonal of rational function R(x,y,z,w,t) = 1/(1 - (x+y+z+w + t*x*y*z*w)) with respect to x,y,z,w, i.e., T(n,k) = [(xyzw)^n*t^k] R(x,y,z,w,t). %C A318105 Annihilating differential operator: x^2*(3*t*x + 1)^2*((t*x - 1)^4 - 256*x)*Dx^3 + 3*x*(3*t*x + 1)*((t*x - 1)^3*(6*t^2*x^2 + 3*t*x - 1) - 384*x*(t*x + 1))*Dx^2 + (t*x - 1)*((t*x - 1)*(63*t^4*x^4 + 66*t^3*x^3 - 18*t*x + 1) + 48*x*(15*t*x + 17))*Dx + (t*x - 1)*(t*(9*t^4*x^4 + 12*t^3*x^3 + 6*t^2*x^2 - 12*t*x + 1) - 24*(15*t*x - 1)). %H A318105 Gheorghe Coserea, <a href="/A318105/b318105.txt">Rows n=0..100, flattened</a> %F A318105 Let P_n(t) = Sum_{k=0..n} T(n,k)*t^k. Then A125143(n) = P_n(-27), A008977(n) = P_n(0), A082488(n) = P_n(1). %e A318105 A(x;t) = 1 + (24 + t)*x + (2520 + 120*t + t^2)*x^2 + (369600 + 22680*t + 360*t^2 + t^3)*x^3 + ... %e A318105 Triangle starts: %e A318105 n\k [0] [1] [2] [3] [4] [5] [6] %e A318105 [0] 1; %e A318105 [1] 24, 1; %e A318105 [2] 2520, 120, 1; %e A318105 [3] 369600, 22680, 360, 1; %e A318105 [4] 63063000, 4804800, 113400, 840, 1; %e A318105 [5] 11732745024, 1072071000, 33633600, 415800, 1680, 1; %e A318105 [6] 2308743493056, 246387645504, 9648639000, 168168000, 1247400, 3024, 1; %e A318105 [7] ... %t A318105 t[n_,k_] := (4*n - 3*k)!/((n-k)!^4*k!); Table[t[n, k], {n, 0, 10}, {k , 0,n}] // Flatten (* _Amiram Eldar_, Nov 07 2018 *) %o A318105 (PARI) T(n, k) = (4*n-3*k)!/(k!*(n-k)!^4); %o A318105 concat(vector(8, n, vector(n, k, T(n-1, k-1)))) %o A318105 /* %o A318105 test: %o A318105 P(n, v='t) = subst(Polrev(vector(n+1, k, T(n, k-1)), 't), 't, v); %o A318105 diag(expr, N=22, var=variables(expr)) = { %o A318105 my(a = vector(N)); %o A318105 for (k = 1, #var, expr = taylor(expr, var[#var - k + 1], N)); %o A318105 for (n = 1, N, a[n] = expr; %o A318105 for (k = 1, #var, a[n] = polcoef(a[n], n-1))); %o A318105 return(a); %o A318105 }; %o A318105 apply_diffop(p, s) = { %o A318105 s=intformal(s); %o A318105 sum(n=0, poldegree(p, 'Dx), s=s'; polcoef(p, n, 'Dx) * s); %o A318105 }; %o A318105 \\ diagonal property: %o A318105 x='x; y='y; z='z; w='w; t='t; %o A318105 diag(1/(1 - (x+y+z+w + t*x*y*z*w)), 9, [x, y, z, w]) == vector(9, n, P(n-1)) %o A318105 \\ annihilating diffop: %o A318105 y = Ser(vector(101, n, P(n-1)), 'x); %o A318105 p = x^2*(3*t*x + 1)^2*((t*x - 1)^4 - 256*x)*Dx^3 + 3*x*(3*t*x + 1)*((t*x - 1)^3*(6*t^2*x^2 + 3*t*x - 1) - 384*x*(t*x + 1))*Dx^2 + (t*x - 1)*((t*x - 1)*(63*t^4*x^4 + 66*t^3*x^3 - 18*t*x + 1) + 48*x*(15*t*x + 17))*Dx + (t*x - 1)*(t*(9*t^4*x^4 + 12*t^3*x^3 + 6*t^2*x^2 - 12*t*x + 1) - 24*(15*t*x - 1)); %o A318105 0 == apply_diffop(p, y) %o A318105 */ %Y A318105 Cf. A008977, A082488, A125143, A318107. %K A318105 nonn,tabl %O A318105 0,2 %A A318105 _Gheorghe Coserea_, Oct 15 2018