A253284 Triangle read by rows, T(n,k) = (k+1)*(n+1)!*(n+k)!/((k+1)!^2*(n-k)!) with n >= 0 and 0 <= k <= n.

1, 2, 2, 6, 18, 12, 24, 144, 240, 120, 120, 1200, 3600, 4200, 1680, 720, 10800, 50400, 100800, 90720, 30240, 5040, 105840, 705600, 2116800, 3175200, 2328480, 665280, 40320, 1128960, 10160640, 42336000, 93139200, 111767040, 69189120, 17297280

Offset

0,2

Comments

G_n(x) = - Sum_{k=0..n} T(n,k)/(x-1)^(n+k+1) are generating functions, for n=0 of A000012, for n=1 of A002378, for n=2 of A083374 (with offset 0) and for n=3 for A253285. In general G_n(x) is the generating function of the sequence k -> ((n+k)!/k!)*C(n+k-1,k-1). These sequences are associated with the rows of the square array of unsigned Lah numbers (compare A253283 for the columns).

Links

Table of n, a(n) for n=0..35.

Formula

T(n,k) = (n+1)!*binomial(n+k,n)*binomial(n,k)/(k+1).

T(n,k) = (n+1)!*A088617(n,k).

T(n,0) = n! = A000142(n).

T(n,1) = A001804(n+1) for n>0.

T(n,n) = (2*n)!/n! = A001813(n).

Sum_{k=0..n} T(n,k) = (n+1)!*hypergeom([-n, n+1], [2], -1) = (n+1)!*A006318(n).

Example

Triangle begins:
1;
2, 2;
6, 18, 12;
24, 144, 240, 120;
120, 1200, 3600, 4200, 1680;
720, 10800, 50400, 100800, 90720, 30240;
5040, 105840, 705600, 2116800, 3175200, 2328480, 665280.

Maple

T := (n, k) -> ((k+1)*(n+1)!*(n+k)!)/((k+1)!^2*(n-k)!);
for n from 0 to 6 do seq(T(n, k), k=0..n) od;

Mathematica

f[n_] := Rest@ Flatten@ Reap@ Block[{i, k, t}, For[i = 0, i <= n, i++, For[k = 0, k <= i, k++, Sow[(i + 1)!*Binomial[i + k, i]*Binomial[i, k]/(k + 1)]]]]; f@ 7 (* Michael De Vlieger, Mar 23 2015 *)

Prog

(PARI) tabl(nn) = {for (n=0, nn, for (k=0, n, print1((n+1)!*binomial(n+k, n)*binomial(n, k)/(k+1), ", "); ); print(); ); } \\ Michel Marcus, Mar 23 2015
(Magma) /* As triangle: */ [[(k + 1)*Factorial(n + 1)*Factorial(n + k)/(Factorial(k + 1)^2*Factorial(n - k)): k in [0..n]]: n in [0..10]]; // Bruno Berselli, Mar 23 2015

Crossrefs

Cf. A000142, A001804, A001813, A002378, A006318, A083374, A088617, A253283, A253285.

Sequence in context: A178882 A186195 A256215 * A176754 A365103 A357537

Adjacent sequences: A253281 A253282 A253283 * A253285 A253286 A253287

Keyword

nonn,tabl,easy

Author

Peter Luschny, Mar 23 2015

Status

approved