A095415 Length of repunits of which the prime factor-digit-excess computed by A095414 equals 0.

2, 3, 5, 7, 9, 11, 13, 17, 19, 23, 27, 31, 47, 59, 67, 71, 83, 113, 127, 139, 163, 197, 211, 229, 251, 263, 311, 317, 347, 421, 457, 461

Offset: 1

Author

Labos Elemer, Jun 22 2004

Keywords

• nonn
• more
• base

Comments

541, 701, 857 are also terms. Conjecture: Except for the number 4, A046413 is a subsequence. Conjecture: except for the prime powers 9 and 27, all terms are prime. - Chai Wah Wu, Nov 03 2019

Sequence continues as 467?, 479?, 509?, 541, 557?, 571?, 577?, 593?, 599?, 617?, 643?, 647?, 661?, 673?, 683?, 691?, 701, 727?, 743?, 751?, 757?, 769?, 773?, 821?, 857, 863?, 887?, 911?, 967?, 971?, 977?, 991?, where ? marks uncertain/candidate terms. - Max Alekseyev, Apr 29 2022

Crossrefs

A004023 is a subsequence.

Cf. A002275, A004023, A095370, A095407, A095413-A095418.

Programs

Mathematica

d[1] = -1; d[n_] := Total[ IntegerLength /@ First /@ FactorInteger[(10^n - 1)/9]] - n; Select[ Range[67], d[#] == 0 &] (* Giovanni Resta, Jul 16 2018 *)

Formula

Solutions to A095414(x) = 0.

Extensions

Data corrected and extended by Giovanni Resta, Jul 16 2018

a(29)-a(32) confirmed by Max Alekseyev, Apr 29 2022