OFFSET
2,1
FORMULA
G.f.: x^2 * (x+2) / ((1-x^3)*(1-x)^2).
Conjecture: a(n) = n + (n^2 mod 3) + a(n-1). - Jon Maiga, Aug 02 2019
a(n) = ceiling((1/2)*(sqrt(3*n^4 + 2*n^3 - 3*n^2 - 2*n + 3)/sqrt(3) - 1)) = (3*n+4)*(n-1)/6 + ((n+2) mod 3)/3. - Rick Mabry, Jul 01 2023
MATHEMATICA
Table[Total[Table[IntegerExponent[2^(n - k) 4^k, 8], {k, 0, n}]], {n, 2, 100}] (* Fred Daniel Kline, Jun 05 2012 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Extended according to the g.f. by R. J. Mathar, Aug 18 2008
STATUS
approved