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A069250 Sum of the reversals of the proper divisors of n.

%I A069250 #21 May 22 2025 10:21:34
%S A069250 0,1,1,3,1,6,1,7,4,8,1,16,1,10,9,15,1,21,1,13,11,14,1,45,6,34,13,55,1,
%T A069250 69,1,76,15,74,13,127,1,94,35,23,1,72,1,40,69,35,1,148,8,61,75,100,1,
%U A069250 174,17,145,95,95,1,99,1,16,32,99,37,78,1,121,36,110,1,240,1,76,112,181,19,198,1,88,85,17,1,203
%N A069250 Sum of the reversals of the proper divisors of n.
%H A069250 Indranil Ghosh, <a href="/A069250/b069250.txt">Table of n, a(n) for n = 1..50000</a>
%H A069250 Pe, J. <a href="http://www.numeratus.net/enlightened/pictureperfect.html">The Picture-Perfect Numbers</a>
%F A069250 a(n) = A069192(n) - A004086(n). - _Indranil Ghosh_, Feb 10 2017
%e A069250 The proper divisors of 20 are 1,2,4,5,10, which reversed are 1,2,4,5,1, summing to 13. Therefore a(20) = 13.
%t A069250 f[n_] := FromDigits[Reverse[IntegerDigits[n]]]; g[n_] := Apply[Plus, Map[f, Drop[Divisors[n], -1]]]; Table[g[i], {i, 1, 40}]
%t A069250 Table[Total[IntegerReverse/@Most[Divisors[n]]],{n,100}] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Apr 04 2021 *)
%o A069250 (Python)
%o A069250 def A069250(n):
%o A069250     s=0
%o A069250     for i in range(1,n):
%o A069250         if n%i==0: s+=int(str(i)[::-1])
%o A069250     return s # _Indranil Ghosh_, Feb 10 2017
%Y A069250 Cf. A069192, A000203, A004086.
%K A069250 base,nonn
%O A069250 1,4
%A A069250 _Joseph L. Pe_, Apr 19 2002
%E A069250 More terms from _N. J. A. Sloane_, May 19 2013