OFFSET
0,3
FORMULA
G.f.: Sum_{k>=1} x^(k^4)/(1 - x)^2. - Ilya Gutkovskiy, Dec 22 2016
a(n) = -(1/30) * floor(n^(1/4)) * (-31 - 30 * n + 10 * floor(n^(1/4))^2 + 15 * floor(n^(1/4))^3 + 6 * floor(n^(1/4))^4). - Pooya Farshim, Sep 28 2024
PROG
(PARI) a(n) = sum(k=1, n, sqrtnint(k, 4)); \\ Michel Marcus, Mar 12 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Tixier (tixier(AT)dyadel.net)
EXTENSIONS
NAME adapted to offset. - Giovanni Resta, May 08 2020
STATUS
approved