OFFSET
0,2
FORMULA
a(n) = 4^n/2 + 2^n*c - c^2/2; where c is (n choose n/2) for even n, 0 for odd n.
EXAMPLE
a(2)=14 because of the 16 ordered pairs, only (00,11) and (11,00) do not qualify.
CROSSREFS
KEYWORD
nonn
AUTHOR
Jon Perry, May 31 2003
EXTENSIONS
Edited by Don Reble, Nov 07 2005
STATUS
approved