A101003 Indices of primes in sequence defined by A(0) = 97, A(n) = 10*A(n-1) - 43 for n > 0.

0, 2, 3, 14, 152, 321, 470, 560, 663, 2156, 3696, 14874, 19269, 22094

Offset

1,2

Comments

Numbers n such that (830*10^n + 43)/9 is prime.

Numbers n such that digit 9 followed by n >= 0 occurrences of digit 2 followed by digit 7 is prime.

Numbers corresponding to terms <= 663 are certified primes.

a(15) > 10^5. - Robert Price, Nov 02 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..14.

Makoto Kamada, Prime numbers of the form 922...227.

Index entries for primes involving repunits.

Formula

a(n) = A103095(n) - 1.

Example

92227 is prime, hence 3 is a term.

Mathematica

Select[Range[0, 100000], PrimeQ[(830*10^# + 43)/9] &] (* Robert Price, Nov 02 2015 *)

Prog

(PARI) a=97; for(n=0, 1000, if(isprime(a), print1(n, ", ")); a=10*a-43)
(PARI) for(n=0, 1000, if(isprime((830*10^n+43)/9 ), print1(n, ", ")))

Crossrefs

Cf. A000533, A002275, A103095.

Sequence in context: A308128 A006279 A041521 * A042071 A042817 A224848

Adjacent sequences: A101000 A101001 A101002 * A101004 A101005 A101006

Keyword

nonn,hard,more,less

Author

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 27 2004

Extensions

Two more terms, corresponding to probable primes, from Ryan Propper, Jun 21 2005

Edited by T. D. Noe, Oct 30 2008

a(12)-a(14) from Kamada data by Ray Chandler, Apr 28 2015

Status

approved