OFFSET
1,3
COMMENTS
Number of 2-r stable discrete function classes on [n] under reversal and complement to n+1.
f(n) == 2 (mod 4) if n == 5 mod 8, otherwise (except for n=2) f(n) == 0 (mod 4). - Robert Israel, Aug 09 2016
LINKS
Robert Israel, Table of n, a(n) for n = 1..700
MAPLE
f:= n -> ((-1)^n - 1 + 2*(n^floor((n + 1)/2)))/4:
map(f, [$1..30]); # Robert Israel, Aug 09 2016
MATHEMATICA
Table[1/4 ((-1)^ n-1+2 (n)^Floor[(n+1)/2]), {n, 1, 20}]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Olivier Gérard, Aug 02 2016
STATUS
approved