A230768 Numbers n such that n = reversal(sigma(n)) - 2.

21, 291, 2991, 43954, 211552, 439954, 880099, 43564354, 43999954, 464057476, 43999999954, 435600004354, 439560043954, 439999999954

Offset

1,1

Comments

A230021 is a subsequence of this sequence. A term n of this sequence is in the sequence A230021 iff 10 does not divide sigma(n). 880099 is in the sequence and sigma(880099) = 1010880, hence 880099 is not in the sequence A230021. What is the next such term of the sequence?

a(11) > 6*10^8. - Farideh Firoozbakht, Feb 05 2014

a(15) > 10^12. - Giovanni Resta, Feb 05 2014

Links

Table of n, a(n) for n=1..14.

Mathematica

Do[If[n==FromDigits[Reverse[IntegerDigits[DivisorSigma[1, n]]]]-2, Print[n]], {n, 310000000}]

Crossrefs

Cf. A000203, A004086, A230021.

Sequence in context: A101703 A102018 A086947 * A230021 A101700 A275359

Adjacent sequences: A230765 A230766 A230767 * A230769 A230770 A230771

Keyword

base,nonn

Author

Jahangeer Kholdi, Feb 04 2014

Extensions

a(10) from Farideh Firoozbakht, Feb 05 2014

a(11)-a(14) from Giovanni Resta, Feb 05 2014

Status

approved