A342021 Numbers k such that A003415(sigma(k)) = k, where A003415 is the arithmetic derivative, and sigma is the sum of divisors of n.

5, 8, 41, 47057

Offset: 1

Author

Antti Karttunen, Apr 08 2021

Keywords

• nonn
• more
• hard

Comments

a(5) > 2^33, if it exists.

Terms of this sequence and A230165 group into pairs (m, sigma(m)), where m is a term of this sequence and sigma(m) is a term of A230165. - Max Alekseyev, Feb 13 2025

Crossrefs

Fixed points of A342925.

Positions of 0's in A342926.

Subsequence of A343217.

Cf. A000203, A003415, A229342, A230164, A230165, A347889.

Formula

a(n) = A003415(A230165(n)). - Max Alekseyev, Feb 13 2025