OFFSET
0,3
FORMULA
Sum_{n>=0} a(n) * x^n / (n!)^2 = BesselJ(0,2*sqrt(x)) * (Ei(x) - log(x) - gamma).
MATHEMATICA
Table[Sum[(-1)^k Binomial[n, k]^2 (n - k - 1)!, {k, 0, n - 1}], {n, 0, 23}]
nmax = 23; Assuming[x > 0, CoefficientList[Series[BesselJ[0, 2 Sqrt[x]] (ExpIntegralEi[x] - Log[x] - EulerGamma), {x, 0, nmax}], x]] Range[0, nmax]!^2
PROG
(PARI) a(n) = sum(k=0, n-1, (-1)^k * binomial(n, k)^2 * (n-k-1)!); \\ Michel Marcus, Mar 06 2022
CROSSREFS
KEYWORD
sign
AUTHOR
Ilya Gutkovskiy, Mar 06 2022
STATUS
approved