OFFSET
1,3
COMMENTS
Inverse Moebius transform of quarter-squares (A002620).
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
MAPLE
f:= proc(n) local d;
add(floor(d^2/4), d=numtheory:-divisors(n))
end proc:
map(f, [$1..100]); # Robert Israel, Dec 28 2023
MATHEMATICA
Table[Sum[Floor[d^2/4], {d, Divisors[n]}], {n, 1, 60}]
nmax = 60; CoefficientList[Series[Sum[x^(2 k)/((1 + x^k) (1 - x^k)^3), {k, 1, nmax}], {x, 0, nmax}], x] // Rest
PROG
(PARI) a(n) = sumdiv(n, d, d^2\4); \\ Michel Marcus, Aug 03 2021
CROSSREFS
KEYWORD
nonn,look
AUTHOR
Ilya Gutkovskiy, Aug 02 2021
STATUS
approved