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A095415
Length of repunits of which the prime factor-digit-excess computed by A095414 equals 0.
3
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
1,1
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
FORMULA
Solutions to A095414(x) = 0.
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 *)
CROSSREFS
A004023 is a subsequence.
Sequence in context: A070566 A325623 A136327 * A326149 A301987 A353393
KEYWORD
nonn,more,base
AUTHOR
Labos Elemer, Jun 22 2004
EXTENSIONS
Data corrected and extended by Giovanni Resta, Jul 16 2018
a(29)-a(32) confirmed by Max Alekseyev, Apr 29 2022
STATUS
approved