login
Number of distinct prime factors of record setting repunits (A328899).
5

%I #24 Aug 04 2023 01:18:16

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

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

%C 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

%t 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

%t (* or, based on the b-file of A095370: *)

%t 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 *)

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

%K nonn,more,base,hard

%O 1,3

%A _Labos Elemer_, Jun 04 2004

%E Data corrected by _Ray Chandler_ and _N. J. A. Sloane_, May 03 2017

%E Name edited by _Giovanni Resta_, Oct 30 2019

%E a(20)-a(21) from _Chai Wah Wu_, Oct 30 2019

%E a(22)-a(23) from _Chai Wah Wu_, Nov 01 2019