A101735 Indices of primes in sequence defined by A(0) = 43, A(n) = 10*A(n-1) + 53 for n > 0.

0, 3, 9, 11, 12, 39, 75, 122, 500, 647, 3540, 4001, 4227, 5270, 7431, 27305, 43401

Offset

1,2

Comments

Numbers n such that (440*10^n - 53)/9 is prime.

Numbers n such that digit 4 followed by n >= 0 occurrences of digit 8 followed by digit 3 is prime.

Numbers corresponding to terms <= 647 are certified primes.

a(18) > 10^5. - Robert Price, Jun 01 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..17.

Makoto Kamada, Prime numbers of the form 488...883.

Index entries for primes involving repunits.

Formula

a(n) = A102998(n) - 1.

Example

48883 is prime, hence 3 is a term.

Mathematica

Select[Range[0, 1000], PrimeQ[(440*10^# - 53)/9] &] (* Robert Price, Jun 01 2015 *)

Prog

(PARI) a=43; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+53)
(PARI) for(n=0, 1500, if(isprime((440*10^n-53)/9), print1(n, ", ")))

Crossrefs

Cf. A000533, A002275, A102998.

Sequence in context: A174565 A074261 A059868 * A101620 A235583 A287333

Adjacent sequences: A101732 A101733 A101734 * A101736 A101737 A101738

Keyword

nonn,hard,more

Author

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

Extensions

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

a(16)-a(17) from Kamada data by Ray Chandler, May 01 2015

Status

approved