OFFSET
1,4
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..20000
FORMULA
G.f.: Sum_{k>=1} a(k)^2 * x^(k^2) / (1 - x^k).
a(4^n) = A067868(n).
MATHEMATICA
a[1] = 1; a[n_] := a[n] = DivisorSum[n, a[#]^2 &, # <= Sqrt[n] &]; Table[a[n], {n, 90}]
PROG
(PARI) A348955(n) = if(1==n, n, sumdiv(n, d, if((d*d)<=n, A348955(d)^2, 0))); \\ Antti Karttunen, Nov 05 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Nov 04 2021
STATUS
approved