A102030 Indices of primes in sequence defined by A(0) = 13, A(n) = 10*A(n-1) + 53 for n > 0.

0, 15, 21, 27, 33, 89, 2067, 2373, 2853, 3719, 4241, 22665, 29291, 29507

Offset

1,2

Comments

Numbers n such that (170*10^n - 53)/9 is prime.

Numbers n such that digit 1 followed by n >= 0 occurrences of digit 8 followed by digit 3 is prime.

Numbers corresponding to terms <= 89 are certified primes.

a(15) > 10^5. - Robert Price, Feb 11 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 188...883.

Index entries for primes involving repunits.

Formula

a(n) = A102944(n) - 1.

Example

13 is prime, hence 0 is a term.

Prog

(PARI) a=13; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+53)
(PARI) for(n=0, 1500, if(isprime((170*10^n-53)/9), print1(n, ", ")))

Crossrefs

Cf. A000533, A002275, A102944.

Sequence in context: A072974 A226025 A082686 * A168104 A026048 A195527

Adjacent sequences: A102027 A102028 A102029 * A102031 A102032 A102033

Keyword

nonn,hard,more

Author

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 28 2004

Extensions

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008

a(12)-a(14) derived from A102944 by Robert Price, Feb 11 2015

Status

approved