A101063 Indices of primes in sequence defined by A(0) = 87, A(n) = 10*A(n-1) - 43 for n > 0.

1, 19, 32, 61, 67, 85, 194, 523, 529, 656, 1873, 2197, 62071, 73075

Offset

1,2

Comments

Numbers n such that (740*10^n + 43)/9 is prime.

Numbers n such that digit 8 followed by n >= 0 occurrences of digit 2 followed by digit 7 is prime.

Numbers corresponding to terms <= 656 are certified primes.

a(15) > 10^5. - Robert Price, Oct 19 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..14.

Makoto Kamada, Prime numbers of the form 822...227.

Index entries for primes involving repunits.

Formula

a(n) = A103076(n+1) - 1. - Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008

Example

827 is prime, hence 1 is a term.

Mathematica

Select[Range[0, 100000], PrimeQ[(740*10^# + 43)/9] &] (* Robert Price, Oct 19 2015 *)

Prog

(PARI) a=87; for(n=0, 1000, if(isprime(a), print1(n, ", ")); a=10*a-43)
(PARI) for(n=0, 1000, if(isprime((740*10^n+43)/9), print1(n, ", ")))

Crossrefs

Cf. A000533, A002275, A103076.

Sequence in context: A160220 A133151 A184750 * A061962 A272910 A116168

Adjacent sequences: A101060 A101061 A101062 * A101064 A101065 A101066

Keyword

nonn,hard,more

Author

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 30 2004

Extensions

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

a(13)-a(14) from Robert Price, Oct 19 2015

Status

approved