OFFSET
1,2
REFERENCES
Colin Defant, Highly sorted permutations and Bell numbers, ECA 1:1 (2021) Article S2R6.
LINKS
Colin Defant, Highly Sorted Permutations and Bell Numbers, arXiv:2012.03869 [math.CO], 2020.
FORMULA
E.g.f.: exp(exp(x) - 1) + exp(x) * (x - 2) + 1. - Ilya Gutkovskiy, Dec 08 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Dec 07 2020
STATUS
approved