A101968 Indices of primes in sequence defined by A(0) = 29, A(n) = 10*A(n-1) - 11 for n > 0.

0, 3, 33, 35, 41, 51, 162, 207, 215, 1416, 14645, 22793, 25647, 32514, 51420

Offset

1,2

Comments

Numbers n such that (250*10^n + 11)/9 is a prime.

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

Numbers corresponding to terms <= 215 are certified primes.

a(16) > 10^5. - Robert Price, Mar 12 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..15.

Makoto Kamada, Prime numbers of the form 277...779.

Index entries for primes involving repunits.

Formula

a(n) = A102959(n) - 1.

Example

27779 is a prime, hence 3 is a term.

Mathematica

Flatten[Position[NestList[10#-11&, 29, 1500], _?PrimeQ]]-1 (* Harvey P. Dale, Oct 14 2013 *)

Prog

(PARI) a=29; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-11)
(PARI) for(n=0, 1500, if(isprime((250*10^n+11)/9), print1(n, ", ")))

Crossrefs

Cf. A000533, A002275, A102959.

Sequence in context: A077328 A106413 A284064 * A103862 A180245 A084502

Adjacent sequences: A101965 A101966 A101967 * A101969 A101970 A101971

Keyword

nonn,hard,more

Author

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 23 2004

Extensions

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

A(11)-a(15) derived from A102959 by Robert Price, Mar 12 2015

Status

approved