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

1,4

Links

Indranil Ghosh, Table of n, a(n) for n = 1..50000

Pe, J. The Picture-Perfect Numbers

Formula

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

Example

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.

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 *)

Prog

(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

Crossrefs

Cf. A069192, A000203, A004086.

Sequence in context: A117552 A294886 A357698 * A294888 A364858 A001065

Adjacent sequences: A069247 A069248 A069249 * A069251 A069252 A069253

Keyword

base,nonn

Author

Joseph L. Pe, Apr 19 2002

Extensions

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

Status

approved