A342923 Numbers k such that A342925(k) = k + 3*A003415(k).

120, 672, 963, 1036, 264768, 523776, 459818240, 1476304896

Offset: 1

Author

Antti Karttunen, Apr 08 2021

Keywords

• nonn
• more

Comments

2^33 < a(9) <= A005820(6) = 51001180160.

Crossrefs

Cf. A003415, A342922, A342925.

Cf. A005820 (subsequence).

Programs

Mathematica

Select[Range[6*10^5], #3 == #1 + 3 #2 & @@ Prepend[Map[If[# < 2, 0, # Total[#2/#1 & @@@ FactorInteger[#]]] &, {#, DivisorSigma[1, #]}], #] &] (* Michael De Vlieger, Feb 25 2022 *)

PARI

A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));
A342925(n) = A003415(sigma(n));
isA342923(n) = (A342925(n)==(n+(3*A003415(n))));

Extensions

a(8) from Antti Karttunen, Feb 25 2022