OFFSET
1,2
COMMENTS
A singly defective permutation omits one value and repeats another value.
a(1) is zero because there are no defective permutations of a single element.
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..500
FORMULA
Conjecture: a(n) = n * (3*n-4) * 2^(n-3) for n > 1. - Andrew Howroyd, May 12 2020
EXAMPLE
Some solutions for n=3 with 1 maximum:
(3,3,2) (1,3,3) (1,1,2) (2,1,1) (3,3,1) (1,3,1) (1,2,2) (2,2,1) (2,2,3).
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 03 2011
EXTENSIONS
Terms a(16) and beyond from Andrew Howroyd, May 12 2020
STATUS
approved