A101581 Indices of primes in sequence defined by A(0) = 59, A(n) = 10*A(n-1) - 41 for n > 0.

0, 2, 3, 5, 9, 20, 29, 71, 198, 207, 269, 395, 618, 758, 1076, 1382, 1565, 1959, 2652, 3503, 3785, 6084, 13109, 36447, 39581, 47988, 50997, 66728

Offset

1,2

Comments

Numbers n such that (490*10^n + 41)/9 is prime.

Numbers n such that digit 5 followed by n >= 0 occurrences of digit 4 followed by digit 9 is prime.

Numbers corresponding to terms <= 758 are certified primes.

a(29) > 10^5. - Robert Price, Jul 21 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..28.

Makoto Kamada, Prime numbers of the form 544...449.

Index entries for primes involving repunits.

Formula

a(n) = A103016(n) - 1.

Example

5449 is prime, hence 2 is a term.

Mathematica

Select[Range[0, 100000], PrimeQ[(490*10^# + 41)/9] &] (* Robert Price, Jul 21 2015 *)

Prog

(PARI) a=59; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-41)
(PARI) for(n=0, 1500, if(isprime((490*10^n+41)/9), print1(n, ", ")))

Crossrefs

Cf. A000533, A002275, A103016.

Sequence in context: A113984 A110542 A101542 * A365044 A349676 A287915

Adjacent sequences: A101578 A101579 A101580 * A101582 A101583 A101584

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

a(23)-a(26) from Kamada data by Ray Chandler, Apr 30 2015

a(27)-a(28) from Robert Price, Jul 21 2015

Status

approved