OFFSET
0,2
LINKS
FORMULA
G.f.: (1+2x+2x^2+3x^3)/(1-2x^2). - Michael Somos, Nov 05 2002
Sum_{n>=0} 1/a(n) = 16/7. - Amiram Eldar, Jan 17 2022
MATHEMATICA
Sort[Flatten[{#, 7#}&/@(2^Range[0, 21])]] (* or *) CoefficientList[Series[ (1+2x+2x^2+3x^3)/(1-2x^2), {x, 0, 50}], x] (* Harvey P. Dale, Apr 23 2011 *)
PROG
(PARI) a(n)=if(n<0, 0, if(n<2, 2^n, if(n%2, 7/2, 2)*2^(n\2)))
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved