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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

Table of n, a(n) for n=1..2.

MATHEMATICA

Do[If[FromDigits[Reverse[IntegerDigits[n]]]==DivisorSigma[1, n]+2n, Print[n]], {n, 27000000}]

CROSSREFS

Cf. A000010, A000203, A004086.

Sequence in context: A254774 A254781 A254727 * A180705 A286036 A215814

Adjacent sequences:  A230012 A230013 A230014 * A230016 A230017 A230018

KEYWORD

nonn,base,bref,more

AUTHOR

Farideh Firoozbakht, Nov 15 2013

STATUS

approved

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Last modified December 2 12:01 EST 2021. Contains 349440 sequences. (Running on oeis4.)