OFFSET
0,2
LINKS
Robert Israel, Table of n, a(n) for n = 0..488
FORMULA
a(n) = 1 + Sum_{0<=k<=n-1} hypergeom([1-n+k,n-k],[-n+k],-k). - Robert Israel, Jan 03 2019
MAPLE
f:= proc(n) local k; 1 + add(simplify(hypergeom([1-n+k, n-k], [-n+k], -k)), k=0..n-1) end proc:
map(f, [$0..50]); # Robert Israel, Jan 03 2019
MATHEMATICA
a[n_] := If[n == 0, 1, Sum[(n-k-j)*Binomial[n-k-1+j, j]* (-k)^j/(n-k), {k, 1, n-1}, {j, 0, n-k-1}] + 2];
Table[a[n], {n, 0, 50}] (* Jean-François Alcover, Feb 06 2023 *)
CROSSREFS
KEYWORD
sign
AUTHOR
Wolfdieter Lang, Sep 21 2001
STATUS
approved