OFFSET
1,4
FORMULA
Conjecture. a(n)=1 if n<4, else a(n)=4^[n/4] if n<>4m+3, else a(n)=7*4^([n/4]-1), where [...] denotes the Floor function. (This has been verified up to n=40.)
CROSSREFS
KEYWORD
nonn
AUTHOR
John W. Layman, Apr 27 2007
STATUS
approved