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

1,1

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

Links

Table of n, a(n) for n=1..4.

Formula

a(n) = A003415(A230165(n)). - 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.

Sequence in context: A258786 A192272 A073930 * A130223 A126750 A256401

Adjacent sequences: A342018 A342019 A342020 * A342022 A342023 A342024

Keyword

nonn,more,hard

Author

Antti Karttunen, Apr 08 2021

Status

approved