OFFSET
1,4
LINKS
Lapo Cioni, Luca Ferrari, and Rebecca Smith, Pop Stacks with a Bypass, arXiv:2406.16399 [cs.DM], 2024. See p. 76.
FORMULA
a(1) = 1 and a(n) = Sum_{k=2..ceiling(n/2)} (n-k)!*binomial(n-k-1, k-2) for n > 1.
MATHEMATICA
a[1]=1; a[n_]:=Sum[(n-k)!Binomial[n-k-1, k-2], {k, 2, Ceiling[n/2]}]; Array[a, 24]
CROSSREFS
KEYWORD
nonn
AUTHOR
Stefano Spezia, Jun 30 2024
STATUS
approved