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A070288
a(n) = Sum_{d|n} omega(d)*omega(n/d).
4
0, 0, 0, 1, 0, 2, 0, 2, 1, 2, 0, 6, 0, 2, 2, 3, 0, 6, 0, 6, 2, 2, 0, 10, 1, 2, 2, 6, 0, 12, 0, 4, 2, 2, 2, 14, 0, 2, 2, 10, 0, 12, 0, 6, 6, 2, 0, 14, 1, 6, 2, 6, 0, 10, 2, 10, 2, 2, 0, 26, 0, 2, 6, 5, 2, 12, 0, 6, 2, 12, 0, 22, 0, 2, 6, 6, 2, 12, 0, 14, 3, 2, 0, 26, 2, 2, 2, 10, 0, 26, 2, 6, 2, 2, 2
OFFSET
1,6
LINKS
FORMULA
a(n) = Sum_{prime p|n} A062799(n/p) = Sum_{prime p|n} Sum_{prime q|(n/p)} A000005(n/p/q). - Max Alekseyev, Aug 11 2016
MATHEMATICA
a[n_] := DivisorSum[n, PrimeNu[#] * PrimeNu[n/#] &]; Array[a, 100] (* Amiram Eldar, May 20 2022 *)
PROG
(PARI) for(n=1, 100, print1(sumdiv(n, d, omega(n/d)*omega(d)), ", "))
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, May 12 2002
STATUS
approved