OFFSET
1,2
COMMENTS
a(n) is the number of relations on a set with n elements that are not one-to-one functions.
LINKS
Michael De Vlieger, Table of n, a(n) for n = 1..57
Mohammad K. Azarian, Remarks and Conjectures Regarding Combinatorics of Discrete Partial Functions, Int'l Math. Forum (2022) Vol. 17, No. 3, 129-141.
EXAMPLE
a(1) = 2^(1^2) - 1! = 1;
a(2) = 2^(2^2) - 2! = 14;
a(3) = 2^(3^2) - 3! = 506.
MATHEMATICA
Table[2^(n^2) - n!, {n, 16}] // Flatten
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Mohammad K. Azarian, Jun 04 2021
STATUS
approved