A056262 Indices of primes in sequence defined by A(0) = 77, A(n) = 10*A(n-1) + 17 for n > 0.
1, 3, 85, 111, 169, 565, 1687, 8901, 115809
Offset: 1
Examples
787 is 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 - 787.
- Makoto Kamada, Prime numbers of the form 788...887.
- Index entries for primes involving repunits.
Programs
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PARI
a=77;for(n=0,1700,if(isprime(a),print1(n,","));a=10*a+17)
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PARI
for(n=0,1700,if(isprime((710*10^n-17)/9),print1(n,",")))
Formula
a(n) = A082715(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 05 2007
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
One more term added from PDP table and comments section updated by Patrick De Geest, Nov 02 2014
Edited by Ray Chandler, Nov 05 2014
Comments