A050397 Reversion of sequence of involutions (A000085).
1, -2, 4, -10, 30, -104, 392, -1568, 6520, -27976, 122944, -551680, 2518912, -11684000, 54957216, -261897024, 1263216192, -6164172608, 30416619200, -151750104800, 765364073120, -3902783995520, 20123276097920
Offset: 1
Keywords
Links
- Andrew Howroyd, Table of n, a(n) for n = 1..200
- N. J. A. Sloane, Transforms
- Index entries for reversions of series
Programs
-
Maple
# Using function CompInv from A357588. CompInv(23, n -> simplify(hypergeom([-n/2, (1-n)/2], [], 2))); # Peter Luschny, Oct 05 2022
-
PARI
seq(n)=Vec(serreverse(serlaplace(-1 + exp(x+x^2/2 + O(x*x^n))))) \\ Andrew Howroyd, May 06 2023