A336397 Numbers k such that both k and A122111(k) [its conjugated prime factorization] are Ore's Harmonic numbers (A001599).

1, 6, 753480, 429520946400

Offset

1,2

Comments

The initial four terms were found from the b-file of 937 terms provided in A001599.

There also at least these additional terms present: 439151400324000, 889013810412000, 106713790278732000, that were found from the file of conjectured initial 10000 terms of A001599 provided by David A. Corneth under that entry. However, there might be further terms in the range between.

Note that A122111(889013810412000) = 106713790278732000, and vice versa, which proves that the intersection of A001599 and A088902 (equal to the intersection of A088902 with A336317) is not equal to this sequence, but just a proper subsequence.

Links

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

Prog

(PARI)
isA001599(n) = !((sigma(n, 0)*n)%sigma(n, 1));
isA336397(n) = (isA001599(n) && isA001599(A122111(n)));
\\ Or alternatively, by using standalone program given in A336317:
isA336397(n) = (isA001599(n) && isA336317(n));

Crossrefs

Intersection of A001599 and A336317.

Cf. A088902, A122111.

Sequence in context: A369973 A172823 A182791 * A235589 A340183 A115476

Adjacent sequences: A336394 A336395 A336396 * A336398 A336399 A336400

Keyword

nonn,hard,more

Author

Antti Karttunen, Jul 20 2020

Status

approved