A101583 Indices of primes in sequence defined by A(0) = 59, A(n) = 10*A(n-1) - 21 for n > 0.

0, 1, 2, 9, 24, 28, 33, 72, 75, 76, 650, 883, 937, 1251, 1892, 3341, 4033, 6167, 6215, 6230, 6811, 11045, 15447, 16627, 16917, 18733, 45934

Offset

1,3

Comments

Numbers n such that (510*10^n + 21)/9 is prime.

Numbers n such that digit 5 followed by n >= 0 occurrences of digit 6 followed by digit 9 is prime.

Numbers corresponding to terms <= 937 are certified primes.

a(28) > 10^5. - Robert Price, Sep 05 2015

References

Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.

Links

Table of n, a(n) for n=1..27.

Makoto Kamada, Prime numbers of the form 566...669.

Index entries for primes involving repunits.

Formula

a(n) = A103018(n) - 1.

Example

5669 is prime, hence 2 is a term.

Mathematica

Flatten[Position[NestList[10#-21&, 59, 940], _?PrimeQ]]-1 (* Harvey P. Dale, Aug 22 2012 *)

Prog

(PARI) a=59; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-21)
(PARI) for(n=0, 1500, if(isprime((510*10^n+21)/9), print1(n, ", ")))

Crossrefs

Cf. A000533, A002275, A103018.

Sequence in context: A133469 A323807 A075714 * A339923 A204556 A185669

Adjacent sequences: A101580 A101581 A101582 * A101584 A101585 A101586

Keyword

nonn,more

Author

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 09 2004

Extensions

7 additional terms, corresponding to probable primes, from Ryan Propper, Jun 24 2005. Next term after 6811 is greater than 10,000.

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008

Edited by T. D. Noe, Oct 30 2008

a(27) from Erik Branger May 01 2013 by Ray Chandler, Apr 30 2015

Status

approved