A072228 Numbers k such that k equals the sum of the reverses of the proper divisors of k.
6, 244, 285, 133857, 141635817, 273722772124
Offset: 1
Examples
The proper divisors of 285 are 1, 3, 5, 15, 19, 57, 95, with sum of reverses = 1 + 3 + 5 + 51 + 91 + 75 + 59 = 285. Therefore 285 is anti-perfect.
Programs
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Mathematica
f[n_] := FromDigits[Reverse[IntegerDigits[n]]]; Do[ If[n == Apply[Plus, Map[f, Drop[Divisors[n], -1]]], Print[n]], {n, 2, 10^7}] Select[Range[15*10^7],Total[IntegerReverse[Most[Divisors[#]]]]==#&] (* Requires Mathematica version 10 or later *) (* The program takes a long time to run *) (* Harvey P. Dale, Aug 31 2016 *)
Extensions
One more term from Farideh Firoozbakht, Dec 23 2004
a(6) from Giovanni Resta, Apr 07 2017
Comments