A101573 Indices of primes in sequence defined by A(0) = 51, A(n) = 10*A(n-1) + 11 for n > 0.

1, 8, 11, 14, 25, 44, 61, 79, 127, 325, 493, 613, 709, 1640, 1645, 2102, 8513, 8687

Offset

1,2

Comments

Numbers n such that (470*10^n - 11)/9 is prime.

Numbers n such that digit 5 followed by n >= 0 occurrences of digit 2 followed by digit 1 is prime.

Numbers corresponding to terms <= 709 are certified primes.

a(19) > 10^5. - Robert Price, Jul 04 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..18.

Makoto Kamada, Prime numbers of the form 522...221.

Index entries for primes involving repunits.

Formula

a(n) = A103008(n) - 1.

Example

521 is prime, hence 1 is a term.

Prog

(PARI) a=51; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+11)
(PARI) for(n=0, 1500, if(isprime((470*10^n-11)/9), print1(n, ", ")))

Crossrefs

Cf. A000533, A002275, A103008.

Sequence in context: A287552 A275191 A279776 * A029629 A028394 A188199

Adjacent sequences: A101570 A101571 A101572 * A101574 A101575 A101576

Keyword

nonn,more

Author

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

Extensions

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

Status

approved