A336397 - OEIS

%I #19 Jul 24 2020 10:57:57

%S 1,6,753480,429520946400

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

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

%C 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.

%C 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.

%o (PARI)

%o isA001599(n) = !((sigma(n,0)*n)%sigma(n,1));

%o isA336397(n) = (isA001599(n) && isA001599(A122111(n)));

%o \\ Or alternatively, by using standalone program given in A336317:

%o isA336397(n) = (isA001599(n) && isA336317(n));

%Y Intersection of A001599 and A336317.

%Y Cf. A088902, A122111.

%K nonn,hard,more

%O 1,2

%A _Antti Karttunen_, Jul 20 2020