A086564 Smallest k such that 10^k + 1 has n distinct prime divisors.

0, 4, 3, 11, 9, 36, 15, 33, 39, 69, 63, 45, 171, 117, 243, 105, 150, 135, 165, 255, 231, 210

Offset: 1

Author

Amarnath Murthy, Aug 31 2003

Keywords

• more
• nonn

Comments

a(27) = 330; a(28) = 315; a(23) >= 347. - Max Alekseyev, Jun 18 2023

a(23) <= 385. - Jon E. Schoenfield, Jun 18 2023

Examples

			a(5) = 9 = log_10(1000000001 - 1).
		

Crossrefs

Smallest inverse of A119704.

Cf. A086563.

Programs

Mathematica

Module[{nn=70,pn},pn=PrimeNu/@(10^Range[0,nn]+1);Flatten[Table[Position[pn,n,1,1],{n,12}]]]-1 (* Harvey P. Dale, Jun 10 2023 *)

Formula

a(n) = log_10(A086563(n) - 1).

Extensions

More terms from Sascha Kurz, Sep 22 2003

a(10)-a(12) from David Wasserman, Mar 28 2005

a(13)-a(22) from Max Alekseyev, Apr 27 2010