A101737 Indices of primes in sequence defined by A(0) = 49, A(n) = 10*A(n-1) - 1 for n > 0.

2, 3, 5, 9, 11, 17, 39, 47, 95, 105, 113, 143, 363, 617, 1089, 11369, 59453, 196683

Offset

1,1

Comments

Numbers n such that (440*10^n + 1)/9 is prime.

Numbers n such that digit 4 followed by n >= 0 occurrences of digit 8 followed by digit 9 is prime.

Numbers corresponding to terms <= 617 are certified primes.

a(19) > 2*10^5. - Robert Price, Mar 30 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..18.

Makoto Kamada, Prime numbers of the form 488...889.

Index entries for primes involving repunits.

Formula

a(n) = A103000(n+1) - 1.

Example

4889 is prime, hence 2 is a term.

Mathematica

Select[Range[0, 10000], PrimeQ[(440*10^# + 1)/9] &]

Prog

(PARI) a=49; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-1)
(PARI) for(n=0, 1500, if(isprime((440*10^n+1)/9), print1(n, ", ")))

Crossrefs

Cf. A000533, A002275, A103000.

Sequence in context: A238657 A329327 A329357 * A176550 A364059 A293036

Adjacent sequences: A101734 A101735 A101736 * A101738 A101739 A101740

Keyword

nonn,hard,more

Author

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 14 2004

Extensions

a(16)-a(18) derived from A103000 by Robert Price, Mar 30 2015

Status

approved