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(n^2-n-(2*n^2-2*n)*x+(n^2-n)*x^2)*P(n-2,x) for n >= 4, with P(2,x) = 1, P(3,x) = 3 + 3*x.","mathematica":"P[2, x_] := 1;\nP[3, x_] := 3 + 3*x;\nP[n_, x_] := P[n, x] = Expand[Together[((2*n^2 + n + (2*n^2 + n)*x)*P[n - 1, x] - (n^2 - n - (2*n^2 - 2*n)*x + (n^2 - n)*x^2)*P[n - 2, x])/(n^2 + 2*n - 8)]];\nTable[Reverse[PadRight[CoefficientList[P[n, x], x], n - 1]], {n, 2, 11}] // Flatten","pari":"P(N) = {my(v = vector(N - 1)); v[1] = 1; v[2] = 3 + 3*x; for(n = 4, N, my(i = n - 1); v[i] = ((2*n^2 + n + (2*n^2 + n)*x)*v[i - 1] - (n^2 - n - (2*n^2 - 2*n)*x + (n^2 - n)*x^2)*v[i - 2])/(n^2 + 2*n - 8)); v};\nrow(n, p) = {my(c = Vecrev(p)); c = concat(c, vector(n - 1 - #c)); c = Vecrev(c); c};\nT(N) = {my(v = P(N)); concat(vector(#v, i, row(i + 1, v[i])))};\nT(11)","reading":{"first_row":0,"offset":2,"reversed":true,"trim_zeros":"none","regular_triangle":true}}],"derivation":{"root":"n-bb74f03367de3ec8","steps":[],"edges":[],"text":"A145597"},"headline":"A145597: Generalized Narayana numbers, T(n, k) = 3/(n + 1)*binomial(n + 1, k + 2)*binomial(n + 1, k - 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