OFFSET
1,3
COMMENTS
This sequence is likely to occur with doubled values and offset 0:
A000371(n) - 2^(2^n-1) = 1, 0, 2, 90, 31826, 2147158386, ... - Tilman Piesk, May 24 2024
REFERENCES
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..11
A. J. Macula, Covers of a finite set, Math. Mag., 67 (1994), 141-144.
Eric Weisstein's World of Mathematics, Proper Cover.
FORMULA
a(n) ~ 2^(2^n)/4. - Vaclav Kotesovec, Jul 02 2016
a(n) = A003465(n) - 2^(2^n-2). - Tilman Piesk, May 24 2024
MAPLE
A007537 := proc(n) (1/2)*add((-1)^k*binomial(n, k)*2^(2^(n-k)), k=0..n)-2^(2^n)/4 end;
MATHEMATICA
Table[1/2 Sum[(-1)^k Binomial[n, k]2^(2^(n-k)), {k, 0, n}]-2^2^n/4, {n, 8}] (* Harvey P. Dale, Oct 31 2011 *)
CROSSREFS
KEYWORD
nonn,easy,nice
AUTHOR
EXTENSIONS
One more term from Emeric Deutsch, Aug 01 2005
STATUS
approved