A344773 - OEIS

A344773

Number of divisors d of n for which A342915(d) = A342915(n), where A342915(n) = gcd(1+n, psi(n)).

1, 1, 1, 2, 1, 2, 1, 2, 1, 2, 1, 4, 1, 2, 1, 3, 1, 3, 1, 2, 1, 2, 1, 5, 1, 2, 2, 3, 1, 4, 1, 3, 1, 2, 1, 6, 1, 2, 1, 4, 1, 3, 1, 1, 2, 2, 1, 7, 1, 2, 2, 3, 1, 4, 1, 4, 1, 2, 1, 7, 1, 2, 1, 4, 2, 4, 1, 2, 1, 3, 1, 8, 1, 2, 2, 3, 1, 3, 1, 1, 2, 2, 1, 7, 1, 2, 1, 4, 1, 6, 1, 2, 1, 2, 1, 8, 1, 3, 2, 4, 1, 4, 1, 1, 2

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OFFSET

1,4

LINKS

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

FORMULA

a(n) = Sum_{d|n} [A342915(d) = A342915(n)], where [ ] is the Iverson bracket.

a(n) <= A344771(n).

PROG

(PARI)

A001615(n) = if(1==n, n, my(f=factor(n)); prod(i=1, #f~, f[i, 1]^f[i, 2] + f[i, 1]^(f[i, 2]-1))); \\ After code in A001615

A342915(n) = gcd(1+n, A001615(n));