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A072228 Numbers n such that n = the sum of the reverses of the proper divisors of n. 2
6, 244, 285, 133857, 141635817 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

I call these numbers "anti-perfect" (compare with the picture-perfect numbers A069942). These are all the anti-perfect numbers up to 3 * 10^6.

Next term is greater than 300000000. - Farideh Firoozbakht, Dec 23 2004

a(6) > 10^11. - Donovan Johnson, Dec 27 2013

LINKS

Table of n, a(n) for n=1..5.

EXAMPLE

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.

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 *)

CROSSREFS

Cf. A069942, A101701.

Sequence in context: A156936 A231019 A254009 * A229631 A206307 A229475

Adjacent sequences:  A072225 A072226 A072227 * A072229 A072230 A072231

KEYWORD

base,more,nonn,nice

AUTHOR

Joseph L. Pe, Jul 05 2002

EXTENSIONS

One more term from Farideh Firoozbakht, Dec 23 2004

STATUS

approved

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Last modified March 24 21:58 EDT 2017. Contains 284002 sequences.