OFFSET
2,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 2..1000
FORMULA
a(n) = sum{k=0..floor(n/2), 0^(k(n-2k))*(n-k+1)}. - Paul Barry, Aug 30 2013
G.f. : x^2*(1+2*x+3*x^2-x^4)/((1-x)^2*(1+x)^2).
a(n) = A080512(n) - 1 for n>2.
MATHEMATICA
CoefficientList[Series[(1 + 2 x + 3 x^2 - x^4)/((1 - x)^2 (1 + x)^2), {x, 0, 40}], x] (* Vincenzo Librandi, Jun 24 2014 *)
PROG
(PARI) a(n) = sum(k=0, n\2, 0^(k*(n-2*k))*(n-k+1)); \\ Michel Marcus, Aug 30 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Michel Marcus, Aug 30 2013
STATUS
approved