A101530 Indices of primes in sequence defined by A(0) = 69, A(n) = 10*A(n-1) - 41 for n > 0.

2, 104, 626, 686, 698, 5714, 11390, 11672

Offset

1,1

Comments

Numbers n such that (580*10^n + 41)/9 is prime.

Numbers n such that digit 6 followed by n >= 0 occurrences of digit 4 followed by digit 9 is prime.

Numbers corresponding to terms <= 698 are certified primes.

a(9) > 10^5. - Robert Price, Sep 11 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..8.

Makoto Kamada, Prime numbers of the form 644...449.

Index entries for primes involving repunits.

Formula

a(n) = A103037(n+1) - 1.

Example

6449 is prime, hence 2 is a term.

Mathematica

Select[Range[0, 100000], PrimeQ[(580*10^# + 41)/9] &] (* Robert Price, Sep 11 2015 *)

Prog

(PARI) a=69; for(n=0, 1000, if(isprime(a), print1(n, ", ")); a=10*a-41)
(PARI) for(n=0, 1000, if(isprime((580*10^n+41)/9), print1(n, ", ")))

Crossrefs

Cf. A000533, A002275, A103037.

Sequence in context: A176933 A246775 A281053 * A199945 A346165 A265655

Adjacent sequences: A101527 A101528 A101529 * A101531 A101532 A101533

Keyword

nonn,hard,more

Author

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 06 2004

Extensions

5714 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008

a(7)-a(8) from Kamada data by Ray Chandler, Apr 30 2015

Status

approved