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A230015 Numbers n such that reversal(n) = sigma(n)+2n. 0
2475247, 26522529 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
If p(m) = (1/101)*(25*10^(4m-1)-53) is prime then p(m) is a term of the sequence. a(1) = p(1) and p(2669) is the second term of this form, which is a 10675-digit prime. This implies a(3) exists and a(3) <= 10^10675. a(3) is greater than 10^9.
a(3) > 10^13. - Giovanni Resta, Feb 08 2014
LINKS
MATHEMATICA
Do[If[FromDigits[Reverse[IntegerDigits[n]]]==DivisorSigma[1, n]+2n, Print[n]], {n, 27000000}]
CROSSREFS
Sequence in context: A254774 A254781 A254727 * A180705 A286036 A215814
KEYWORD
nonn,base,bref,more
AUTHOR
Farideh Firoozbakht, Nov 15 2013
STATUS
approved

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Last modified June 17 23:38 EDT 2024. Contains 373468 sequences. (Running on oeis4.)