A095371 Number of distinct prime factors of record setting repunits (A328899).

0, 1, 2, 5, 7, 8, 10, 13, 14, 20, 21, 22, 26, 29, 32, 33, 34, 35, 40, 44, 55, 56, 63

Offset

1,3

Comments

Conjecture: a(24) = 73, a(25) = 94, a(26) = 99, a(27) >= 107, a(28) >= 127, a(29) >= 136, a(30) >= 140, a(31) >= 151, a(32) >= 159, a(33) >= 163, a(34) >= 178, a(35) >= 184, a(36) >= 213, a(37) >= 214. - Chai Wah Wu, Nov 01 2019

Links

Table of n, a(n) for n=1..23.

Mathematica

r[n_] := (10^n-1)/9; L = {}; bst = -1; Do[v = PrimeNu[r[n]]; If[v > bst, bst = v; AppendTo[L, v]], {n, 60}]; L
(* or, based on the b-file of A095370: *)
w = Last /@ Cases[Import["https://oeis.org/A095370/b095370.txt", "Table"], {_Integer, _Integer}]; L = {}; bst = -1; Do[ If[j > bst, AppendTo[L, bst = j]], {j, w}]; L (* Giovanni Resta, Oct 30 2019 *)

Crossrefs

Cf. A067063, A003020, A001221, A002275, A095370, A004023.

Sequence in context: A034028 A268272 A102700 * A047481 A372325 A158704

Adjacent sequences: A095368 A095369 A095370 * A095372 A095373 A095374

Keyword

nonn,more,base,hard

Author

Labos Elemer, Jun 04 2004

Extensions

Data corrected by Ray Chandler and N. J. A. Sloane, May 03 2017

Name edited by Giovanni Resta, Oct 30 2019

a(20)-a(21) from Chai Wah Wu, Oct 30 2019

a(22)-a(23) from Chai Wah Wu, Nov 01 2019

Status

approved