A353371 Number of divisors of n that are not in A325698.

0, 1, 1, 2, 1, 2, 1, 3, 2, 3, 1, 4, 1, 2, 2, 4, 1, 4, 1, 5, 3, 3, 1, 6, 2, 2, 3, 4, 1, 5, 1, 5, 2, 3, 2, 6, 1, 2, 3, 7, 1, 5, 1, 5, 4, 3, 1, 8, 2, 5, 2, 4, 1, 6, 3, 6, 3, 2, 1, 9, 1, 3, 5, 6, 2, 5, 1, 5, 2, 5, 1, 9, 1, 2, 4, 4, 2, 5, 1, 9, 4, 3, 1, 8, 3, 2, 3, 7, 1, 8, 3, 5, 2, 3, 2, 10, 1, 4, 4, 8, 1, 5, 1, 6, 5

Offset

1,4

Links

Antti Karttunen, Table of n, a(n) for n = 1..65537

Index entries for sequences computed from indices in prime factorization

Formula

a(n) = Sum_{d|n} 1-A353370(d).

a(n) = A000005(n) - A353372(n).

a(p) = 1 for all primes p.

a(n) = a(A003961(n)) = a(A348717(n)), for all n >= 1.

Prog

(PARI)
A353370(n) = { my(f = factor(n)); (0==sum(i=1, #f~, f[i, 2]*((-1)^(primepi(f[i, 1])%2)))); };
A353371(n) = sumdiv(n, d, !A353370(d));

Crossrefs

Cf. A000005, A003961, A325698, A348717, A353370, A353372.

Sequence in context: A217743 A238845 A093873 * A353334 A353304 A305974

Adjacent sequences: A353368 A353369 A353370 * A353372 A353373 A353374

Keyword

nonn

Author

Antti Karttunen, Apr 16 2022

Status

approved