A056263 Indices of primes in sequence defined by A(0) = 77, A(n) = 10*A(n-1) + 27 for n > 0.
1, 3, 27, 155, 321, 351, 1211, 1283, 7983, 15191, 84771, 119929, 148859
Offset: 1
Examples
797 is a prime, hence 1 is a term.
References
- Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
Links
- Patrick De Geest, PDP Reference Table - 797.
- Makoto Kamada, Prime numbers of the form 799...997.
- Index entries for primes involving repunits.
Programs
-
PARI
a=77;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a+27)
-
PARI
for(n=0,1500,if(isprime((720*10^n-27)/9),print1(n,",")))
Formula
a(n) = A082716(n) - 2.
Extensions
Additional comments from Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 03 2004
Edited by N. J. A. Sloane at the suggestion of Andrew S. Plewe, Jun 08 2007
Update from De Geest link by Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
a(11)=84771 from Ray Chandler, Jan 04 2011
a(12)=119929 from Ray Chandler, Apr 01 2011
a(13)=148859 from Ray Chandler, Apr 09 2011
Updated comments section by Patrick De Geest, Nov 02 2014
Edited by Ray Chandler, Nov 04 2014
Comments