A116028 Numbers k such that k + sigma(k) + sigma(sigma(k)) is a repdigit.

1, 2, 15, 25, 119, 157, 2413, 2623, 8415, 14962, 18303, 66078, 1031747, 62826675, 692799137, 759500195, 1144100379

Offset

1,2

Comments

a(18) > 5*10^9. - Donovan Johnson, Feb 18 2013

Links

Table of n, a(n) for n=1..17.

Example

1031747 + sigma(1031747) + sigma(sigma(1031747)) = 5555555.

Mathematica

repQ[n_]:=Module[{ds=DivisorSigma[1, n]}, Count[DigitCount[n+ds+ DivisorSigma[ 1, ds]], 0] == 9]; Select[Range[66100], repQ] (* The program generates the first 12 terms of the sequence. To generate more, increase the Range constant, but it will take a long time to run. *) (* Harvey P. Dale, Oct 08 2020 *)

Crossrefs

Cf. A010785, A116017.

Sequence in context: A116049 A184236 A023651 * A175828 A300346 A370031

Adjacent sequences: A116025 A116026 A116027 * A116029 A116030 A116031

Keyword

nonn,base

Author

Giovanni Resta, Feb 13 2006

Extensions

a(14)-a(17) from Donovan Johnson, Feb 18 2013

Status

approved