1,2

f-perfect numbers for an arithmetical function f is defined in A066218.

Also, numbers m such that 3*sigma(m)-2*m = A007429(m). - Max Alekseyev, Jul 30 2025

Joseph L. Pe, On a Generalization of Perfect Numbers, J. Rec. Math., 31(3) (2002-2003), 168-172.

f[x_] := Abs[DivisorSigma[1, x] - x]; Select[ Range[2, 10^6], 2 * f[ # ] == Apply[ Plus, Map[ f, Divisors[ # ] ] ] & ]

Cf. A007429, A066218.

Sequence in context: A122476 A361346 A289253 * A014365 A362543 A027545

Adjacent sequences: A066362 A066363 A066364 * A066366 A066367 A066368

nonn,more

Joseph L. Pe, Dec 21 2001

Edited and a(1)=1 inserted by Max Alekseyev, Jul 30 2025

approved