A101015 Indices of primes in sequence defined by A(0) = 93, A(n) = 10*A(n-1) + 43 for n > 0.

5, 14, 35, 44, 446, 1030, 1238, 3491, 6068, 13646, 17237, 56270, 72710, 75380

Offset

1,1

Comments

Numbers n such that (880*10^n - 43)/9 is prime.

Numbers n such that digit 9 followed by n >= 0 occurrences of digit 7 followed by digit 3 is prime.

Numbers corresponding to terms <= 1030 are certified primes.

a(15) > 10^5. - Robert Price, Nov 12 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 977...773.

Index entries for primes involving repunits.

Formula

a(n) = A103106(n+1) - 1.

Example

9777773 is prime, hence 5 is a term.

Mathematica

Select[Range[0, 100000], PrimeQ[(880*10^# - 43)/9] &] (* Robert Price, Nov 12 2015 *)

Prog

(PARI) a=93; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+43)
(PARI) for(n=0, 1500, if(isprime((880*10^n-43)/9), print1(n, ", ")))

Crossrefs

Cf. A000533, A002275, A103106.

Sequence in context: A047860 A369887 A083332 * A076858 A001215 A335651

Adjacent sequences: A101012 A101013 A101014 * A101016 A101017 A101018

Keyword

nonn,hard,more

Author

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 27 2004

Extensions

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

a(10)-a(11) from Kamada data by Ray Chandler, Apr 29 2015

a(12)-a(14) from Robert Price, Nov 12 2015

Status

approved