A046414 Repunit of length a(n) has exactly 3 prime factors (counted with multiplicity).

13, 31, 37, 38, 67, 73, 83, 97, 101, 103, 113, 127, 149, 163, 191, 227, 241, 263, 313, 331, 373, 379

Offset: 1

Author

Patrick De Geest, Jul 15 1998

Keywords

• nonn
• more
• base

Comments

467 <= a(23) <= 857. 857, 1303, 1483, 2267 are terms of this sequence. - Chai Wah Wu, Nov 03 2019

Examples

			a(n)=13 so 1111111111111 = 53*79*265371653.
		

Links

• P. De Geest, Repunits prime factors
• Makoto Kamada, Factorizations of 11...11 (Repunit)
• Eric Weisstein's World of Mathematics, Repunit

Crossrefs

Cf. A000042, A001222, A002275, A004022, A046053.

Programs

PARI

is(n)=bigomega(10^n\9)==3 \\ Charles R Greathouse IV, Mar 11 2014

Extensions

More terms from Robert Gerbicz, Nov 22 2010

More terms from Bo Gyu Jeong, Jun 12 2012