OFFSET
1,2
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
FORMULA
a(n) = Sum_{k=1..n} ud(k)^2 = Sum_{k=1..n} A034444(k)^2 . a(n) = Sum_{k=1..n} 2^(2*omega(k)) = Sum_{k=1..n} 2^(2*A001221(k)).
a(n) ~ c * n * log(n)^3, where c = (1/6) * Product_{p prime} ((1-1/p)^3*(1+3/p)) = A319592 / 6. - Amiram Eldar, Jul 02 2022
MAPLE
with(numtheory): seq(add(2^(2*nops(ifactors(k)[2])), k=1..n), n=1..100);
MATHEMATICA
Accumulate[Table[Count[Divisors[n], _?(GCD[#, n/#]==1&)], {n, 60}]^2] (* Harvey P. Dale, Dec 06 2012 *)
Accumulate[Table[4^PrimeNu[n], {n, 1, 50}]] (* Amiram Eldar, Jul 02 2022 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Antonio G. Astudillo (afg_astudillo(AT)hotmail.com), Sep 07 2002
STATUS
approved