A101955 Indices of primes in sequence defined by A(0) = 29, A(n) = 10*A(n-1) - 71 for n > 0.

0, 222, 317, 426, 3726, 5226, 8778, 11382, 15414, 26381

Offset

1,2

Comments

Numbers n such that (190*10^n + 71)/9 is prime.

Numbers n such that digit 2 followed by n >= 0 occurrences of digit 1 followed by digit 9 is prime.

Numbers corresponding to terms <= 426 are certified primes.

a(11) > 10^5. - Robert Price, Feb 06 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..10.

Makoto Kamada, Prime numbers of the form 211...119.

Index entries for primes involving repunits.

Formula

a(n) = A102950(n) - 1.

Example

29 is prime, hence 0 is a term.

Prog

(PARI) a=29; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-71)
(PARI) for(n=0, 1500, if(isprime((190*10^n+71)/9), print1(n, ", ")))

Crossrefs

Cf. A000533, A002275, A102950.

Sequence in context: A345521 A345775 A361628 * A063352 A250521 A043499

Adjacent sequences: A101952 A101953 A101954 * A101956 A101957 A101958

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(8)-a(10) derived from A102950 by Robert Price, Feb 06 2015

Status

approved