A101148 Indices of primes in sequence defined by A(0) = 73, A(n) = 10*A(n-1) + 33 for n > 0.

0, 6, 89, 92, 124, 146, 497, 867, 878, 1156, 2957, 3017, 3316, 3821, 6947, 8884, 13091, 33322, 35846, 79491

Offset

1,2

Comments

Numbers n such that (690*10^n - 33)/9 is prime.

Numbers n such that digit 7 followed by n >= 0 occurrences of digit 6 followed by digit 3 is prime.

Numbers corresponding to terms <= 878 are certified primes.

a(21) > 10^5. - Robert Price, Oct 14 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..20.

Makoto Kamada, Prime numbers of the form 766...663.

Index entries for primes involving repunits.

Formula

a(n) = A103064(n) - 1.

Example

73 is prime, hence 0 is a term.

Mathematica

Select[Range[0, 100000], PrimeQ[(690*10^# - 33)/9] &] (* Robert Price, Oct 14 2015 *)

Prog

(PARI) a=73; for(n=0, 1200, if(isprime(a), print1(n, ", ")); a=10*a+33)
(PARI) for(n=0, 1200, if(isprime((690*10^n-33)/9), print1(n, ", ")))
(Magma) [n: n in [0..500] | IsPrime((690*10^n-33) div 9)]; // Vincenzo Librandi, Oct 15 2015

Crossrefs

Cf. A000533, A002275, A103064.

Sequence in context: A309165 A127183 A054952 * A355187 A100297 A177568

Adjacent sequences: A101145 A101146 A101147 * A101149 A101150 A101151

Keyword

nonn,hard,more

Author

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 03 2004

Extensions

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

a(18)-a(19) from Erik Branger May 01 2013 by Ray Chandler, Apr 30 2015

a(20) from Robert Price, Oct 14 2015

Status

approved