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

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, 69, 1, 76, 15, 74, 13, 127, 1, 94, 35, 23, 1, 72, 1, 40, 69, 35, 1, 148, 8, 61, 75, 100, 1, 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

Offset: 1

Author

Joseph L. Pe, Apr 19 2002

Keywords

• base
• nonn

Examples

			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.
		

Links

• Indranil Ghosh, Table of n, a(n) for n = 1..50000
• Pe, J. The Picture-Perfect Numbers

Crossrefs

Cf. A069192, A000203, A004086.

Programs

Mathematica

f[n_] := FromDigits[Reverse[IntegerDigits[n]]]; g[n_] := Apply[Plus, Map[f, Drop[Divisors[n], -1]]]; Table[g[i], {i, 1, 40}]
Table[Total[IntegerReverse/@Most[Divisors[n]]],{n,100}] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Apr 04 2021 *)

Python

def A069250(n):
    s=0
    for i in range(1,n):
        if n%i==0: s+=int(str(i)[::-1])
    return s # Indranil Ghosh, Feb 10 2017

Formula

a(n) = A069192(n) - A004086(n). - Indranil Ghosh, Feb 10 2017

Extensions

More terms from N. J. A. Sloane, May 19 2013