A353761 a(n) = gcd(A353749(n), A353750(n)), where A353749(n) = phi(n)*A064989(n), and A353750(n) = A353749(sigma(n)).

1, 1, 2, 2, 4, 4, 2, 4, 12, 12, 2, 4, 6, 2, 16, 2, 8, 24, 6, 24, 8, 2, 2, 16, 30, 12, 48, 60, 4, 48, 2, 16, 8, 16, 8, 24, 18, 6, 24, 48, 40, 8, 14, 20, 48, 2, 2, 4, 6, 60, 32, 6, 4, 48, 24, 24, 24, 4, 2, 96, 30, 2, 48, 2, 48, 8, 2, 16, 8, 24, 2, 96, 36, 36, 60, 36, 4, 48, 6, 24, 2, 40, 2, 240, 96, 14, 16, 8, 8, 288

Offset: 1

Author

Antti Karttunen, May 10 2022

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..10000
• Antti Karttunen, Data supplement: n, a(n) computed for n = 1..65537
• Index entries for sequences computed from indices in prime factorization
• Index entries for sequences related to sigma(n)

Crossrefs

Cf. A000010, A000203, A006872, A062401, A064989, A336549, A336550, A353757, A353762, A353763.

Programs

PARI

A064989(n) = { my(f=factor(n>>valuation(n,2))); for(i=1, #f~, f[i,1] = precprime(f[i,1]-1)); factorback(f); };
A353749(n) = (eulerphi(n)*A064989(n));
A353761(n) = { my(s=sigma(n)); gcd(A353749(s), A353749(n)); };

Formula

a(n) = gcd(A353749(n), A353750(n)) = gcd(A353749(n), A353757(n)) = gcd(A353750(n), A353757(n)).

a(n) = A353749(n) / A353762(n) = A353750(n) / A353763(n).