login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A046414 Repunit of length a(n) has exactly 3 prime factors (counted with multiplicity). 0
13, 31, 37, 38, 67, 73, 83, 97, 101, 103, 113, 127, 149, 163, 191, 227, 241, 263, 313, 331, 373, 379 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..22.

P. De Geest, Repunits prime factors

Makoto Kamada, Factorizations of 11...11 (Repunit)

Eric Weisstein's World of Mathematics, Repunit

EXAMPLE

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

PROG

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

CROSSREFS

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

Sequence in context: A299130 A156532 A227435 * A023694 A038465 A103665

Adjacent sequences:  A046411 A046412 A046413 * A046415 A046416 A046417

KEYWORD

nonn,more,base

AUTHOR

Patrick De Geest, Jul 15 1998.

EXTENSIONS

More terms from Robert Gerbicz, Nov 22 2010

More terms from Bo Gyu Jeong, Jun 12 2012

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 20 05:01 EDT 2019. Contains 324229 sequences. (Running on oeis4.)