OFFSET
0,3
FORMULA
G.f.: Sum_{k>=1} x^(k^5)/(1 - x)^2. - Ilya Gutkovskiy, Dec 22 2016
a(n) = -(1/12) * floor(n^(1/5)) * (-12 - 12*n - floor(n^(1/5)) + 5*floor(n^(1/5))^3 + 6*floor(n^(1/5))^4 + 2*floor(n^(1/5))^5). - Pooya Farshim, Sep 28 2024
MATHEMATICA
Accumulate[Floor[Surd[Range[0, 70], 5]]] (* Harvey P. Dale, Jan 21 2019 *)
PROG
(PARI) a(n) = sum(k=1, n, sqrtnint(k, 5)); \\ Michel Marcus, Mar 12 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Tixier (tixier(AT)dyadel.net)
STATUS
approved