A101834 Indices of primes in sequence defined by A(0) = 39, A(n) = 10*A(n-1) - 41 for n > 0.

1, 2, 5, 11, 35, 38, 43, 89, 257, 511, 1481, 2377, 2405, 3223, 3377, 3875, 4160, 5509, 7424, 97241

Offset

1,2

Comments

Numbers n such that (310*10^n + 41)/9 is prime.

Numbers n such that digit 3 followed by n >= 0 occurrences of digit 4 followed by digit 9 is prime.

Numbers corresponding to terms <= 511 are certified primes.

a(21) > 10^5. - Robert Price, Apr 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..20.

Makoto Kamada, Prime numbers of the form 344...449.

Index entries for primes involving repunits.

Formula

a(n) = A102970(n) - 1.

Example

3449 is prime, hence 2 is a term.

Mathematica

Select[Range[0, 10000], PrimeQ[(310*10^# + 41)/9] &] (* Robert Price, Apr 04 2015 *)

Prog

(PARI) a=39; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-41)
(PARI) for(n=0, 1500, if(isprime((310*10^n+41)/9), print1(n, ", ")))

Crossrefs

Cf. A000533, A002275, A102970.

Sequence in context: A307316 A298122 A196690 * A117758 A284251 A343162

Adjacent sequences: A101831 A101832 A101833 * A101835 A101836 A101837

Keyword

nonn,hard,more

Author

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 20 2004

Extensions

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

a(20) derived from A102970 by Robert Price, Apr 04 2015

Status

approved