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A072234
Numbers k such that reverse(k) = sum of the proper divisors of k.
3
6, 498906, 20671542, 41673714, 73687923, 4158499614, 922964834547
OFFSET
1,1
COMMENTS
Mark Ganson conjectures that all terms are divisible by 3.
Jens Kruse Andersen discovered that 4158499614 is in the sequence (although he did not rule out the possibility that there were missing terms below this - that was established by Giovanni Resta).
a(8) > 10^13. - Giovanni Resta, Dec 12 2013
EXAMPLE
The proper divisors of 498906 are 1, 2, 3, 6, 9, 18, 27, 54, 9239, 18478, 27717, 55434, 83151, 166302, 249453, which sum to 609894, the reverse of 498906; hence 498906 is a term of the sequence.
MATHEMATICA
f = IntegerReverse; Do[ If[f[n] == Apply[Plus, Drop[Divisors[n], -1]], Print[n]], {n, 2, 10^9}]
PROG
(PARI) for(n=1, 10^9, if(sigma(n)-n==eval(concat(Vecrev(Str(n)))), print1(n, ", "))) \\ Edward Jiang, Sep 10 2014
CROSSREFS
KEYWORD
base,more,nonn,nice
AUTHOR
Joseph L. Pe, Jul 05 2002
EXTENSIONS
a(6) confirmed and a(7) discovered by Giovanni Resta, Dec 12 2013
STATUS
approved