A291821 Central terms of triangle A291820.

1, 2, 38, 1245, 55566, 3062271, 197983540, 14567100211, 1196032764639, 108105913233804, 10651377348228706, 1135394214204504346, 130161542660895451934, 15969338705916554563833, 2088140238440781625249392, 289961586742613652475061397, 42623636996226195002733858964, 6613842247421357561153219091827, 1080515428870235624428208631160409, 185421585676394321869412169323524031

Offset

1,2

Comments

The g.f. F(x,y) of A291820 satisfies: F(x - x*y*F(x,y), y) = x + x*(1-y)*F(x,y).

Links

Paul D. Hanna, Table of n, a(n) for n = 1..50

Formula

a(n) = A291820(2*n-1, n-1) for n>=1.

Prog

(PARI) /* As central terms of triangle A291820 */
{A291820(n, k) = my(A=x); for(i=1, n, A = x + subst(x*A, x, y*A + (1-y)*x +x*O(x^n)) ); polcoeff(polcoeff(A, n, x), k, y)}
for(n=1, 20, print1(A291820(2*n-1, n-1), ", "));

Crossrefs

Cf. A291820.

Sequence in context: A246000 A266601 A266597 * A187544 A187545 A246484

Adjacent sequences: A291818 A291819 A291820 * A291822 A291823 A291824

Keyword

nonn

Author

Paul D. Hanna, Sep 01 2017

Status

approved