OFFSET
0,3
FORMULA
a(n) = n! * [x^n] (exp(2*x) - exp(x))/(exp(x) - 2)^2.
a(n) = Sum_{k=0..n} T(n, k)*k, where T(n, k) = Sum_{j=0..n} Eulerian1(n, j)* binomial(n-j, n-k) is the (0, 0)-based variant of A028246.
a(n) = 2^n*(Epoly(n+1, 1/2) - Epoly(n, 1/2)) where Epoly(n, x) are the Eulerian1 polynomials.
a(n) + 1 = A274273(n).
MAPLE
E1poly := (n, x) -> add(combinat:-eulerian1(n, k)*x^k, k=0..n):
seq(2^n*(E1poly(n+1, 1/2) - E1poly(n, 1/2)), n=0..20);
MATHEMATICA
a[n_] := (PolyLog[-1 - n, 1/2] - 2 PolyLog[-n, 1/2])/2;
Table[a[n], {n, 0, 20}]
PROG
(PARI) a(n) = if (n, polylog(-n-1, 1/2)/2 - polylog(-n, 1/2), 0); \\ Michel Marcus, Apr 26 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Luschny, Apr 26 2021
STATUS
approved