OFFSET
0,3
REFERENCES
J. Riordan, Combinatorial Identities, Wiley, 1968, p. 77.
LINKS
FORMULA
Recurrence: (n-2)*(n-1)*a(n) = -(n-2)*(n+1)*(2*n-1)*a(n-1) + n*(n+1)*a(n-2). - Vaclav Kotesovec, Jul 22 2015
a(n) ~ (-1)^n * 2^(n+1/2) * n^(n+2) / exp(n+1). - Vaclav Kotesovec, Jul 22 2015
From G. C. Greubel, Aug 14 2017: (Start)
a(n) = 2*n*(n-1)*(1/2)_{n}*(-2)^(n - 1)* hypergeometric1f1(2 - n, -2*n, -2), where (a)_{n} is the Pochhammer symbol.
E.g.f.: (1 + 2*x)^(-5/2)*(x*(x + 2)*sqrt(1 + 2*x) + (2*x^3 - 2*x)) * exp(-1 + sqrt(1 + 2*x)). (End)
G.f.: (6*x^2/(1-x)^5)*hypergeometric2f0(3,5/2; - ; -2*x/(1-x)^2). - G. C. Greubel, Aug 16 2017
MATHEMATICA
Table[Sum[(n+k+2)!*(-1)^k/(2^(k+2)*(n-k-2)!*k!), {k, 0, n-2}], {n, 0, 20}] (* Vaclav Kotesovec, Jul 22 2015 *)
Join[{0, 0}, Table[4*n*(n-1)*Pochhammer[1/2, n]*(-2)^(n-2)* Hypergeometric1F1[2-n, -2*n, -2], {n, 2, 20}]] (* G. C. Greubel, Aug 14 2017 *)
PROG
(PARI) for(n=0, 20, print1(sum(k=0, n-2, (n+k+2)!*(-1)^k/(2^(k+2)*(n-k-2)!*k!)), ", ")) \\ G. C. Greubel, Aug 14 2017
(Magma) f:=Factorial; [0, 0] cat [(&+[((-1)^k*f(n+k+2)/(2^(k+2)*f(n-k-2) *f(k))): k in [0..n-2]]): n in [2..20]]; // G. C. Greubel, Jul 10 2019
(Sage) f=factorial; [0, 0]+[sum((-1)^k*f(n+k+2)/(2^(k+2)*f(n-k-2)*f(k)) for k in (0..n-2)) for n in (2..20)] # G. C. Greubel, Jul 10 2019
(GAP) f:=Factorial;; Concatenation([0, 0], List([2..20], n-> Sum([0..n-2], k-> (-1)^k*f(n+k+2)/(2^(k+2)*f(n-k-2)*f(k)) ))); # G. C. Greubel, Jul 10 2019
CROSSREFS
KEYWORD
sign
AUTHOR
N. J. A. Sloane, Dec 08 2001
STATUS
approved