OFFSET
1,4
LINKS
FORMULA
If n is a multiple of 3 then a(n) = 2a(n-1)-A217929(n/3), otherwise a(n) = 2a(n-1).
Comment from Paul Curtz, Oct 15 2012:
From a(n+3)=1, the terms taken in threes are: 1,2,4, 8,16,32, 63,126,252, ... (*).
a(n+4) - 2*a(n+3) = 0,0,0, 0,0,-1, 0,0,-2, 0,0,-4, 0,0,-7, 0,0,-16, 0,0,-30, 0,0,-63, 0,0,-122,... . See -A217929. This is the formula given above.
2^n - (*) = 0,0,0,0,0,0,1,2,4,10,20,40,84,168,336,679,1358,2716,5448,...
= b(n) with offset 0. Hence a second formula:
b(n+1)-2*b(n)=0,0,0,0,0,1,0,0,2,0,0,4,0,0,7,0,0,16,... . (End)
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Oct 15 2012
STATUS
approved