OFFSET
2,1
COMMENTS
Equals the row sums of triangle A326799.
FORMULA
EXAMPLE
E.g.f.: C(x) = 2*x^2/2! - 4*x^4/4! - 154*x^6/6! + 1336*x^8/8! + 139402*x^10/10! - 2516812*x^12/12! - 531298962*x^14/14! + 16291452784*x^16/16! + 5792759106578*x^18/18! - 269619415772564*x^20/20! + ...
PROG
(PARI) {a(n, k) = my(Ax=x, Bx=1, Cx=x, Ay=y, By=y, Cy=1);
for(i=0, 2*n+1,
Ax = 0 + intformal( Bx*Cy - Cx*By, x) + O(x^(2*n+2));
Bx = 1 + intformal( Cx*Ay - Ax*Cy, x) + O(x^(2*n+2));
Cx = 0 + intformal( Ax*By - Bx*Ay, x) + O(x^(2*n+2));
Ay = 0 + intformal( By*Cx - Cy*Bx, y) + O(y^(2*n+2));
By = 0 + intformal( Cy*Ax - Ay*Cx, y) + O(y^(2*n+2));
Cy = 1 + intformal( Ay*Bx - By*Ax, y) + O(y^(2*n+2));
);
sum(k=0, n, (2*n+2)! * polcoeff( polcoeff(Cx, 2*n-2*k+1, x), 2*k+1, y))}
for(n=0, 20, print1( a(n), ", "))
CROSSREFS
KEYWORD
sign
AUTHOR
Paul D. Hanna, Aug 05 2019
STATUS
approved