OFFSET
0,2
FORMULA
a(n)=N(3; k, x=-1), with the polynomials N(3; k, x) from the staircase array A062746.
a(n) = 2*( Sum_{j = 0..n} (-1)^j*C(3; n-j)*4^(n-j) ) - (-1)^n with C(3; n) := A001764(n) = A062993(n+1, 1) (a Pfaff-Fuss or 3-Raney sequence).
G.f.: (2*c(3; 4*x)-1)/(1+x) with c(3; x)= RootOf(x*_Z^3-_Z +1), the g.f. of A001764 [formula for a(n) and g.f. corrected by Peter Bala, Mar 26 2020].
Conjectural recurrence: n*(2*n+1)*a(n) = (4*n-3)*(13*n-4)*a(n-1) + 6*(3*n-1)*(3*n-2)*a(n-2) with a(0) = 1, a(1) = 7. - Peter Bala, Mar 25 2020
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Wolfdieter Lang, Jul 12 2001
STATUS
approved