A102017 Indices of primes in sequence defined by A(0) = 19, A(n) = 10*A(n-1) - 41 for n > 0.

0, 1, 3, 10, 12, 25, 153, 195, 435, 528, 1110, 2562, 2640, 3232, 3882, 4255, 9297, 17292, 23269, 27196

Offset

1,3

Comments

Numbers n such that (130*10^n + 41)/9 is prime.

Numbers n such that digit 1 followed by n >= 0 occurrences of digit 4 followed by digit 9 is prime.

Numbers corresponding to terms <= 528 are certified primes.

a(21) > 10^5. - Robert Price, Apr 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..20.

Makoto Kamada, Prime numbers of the form 144...449.

Index entries for primes involving repunits.

Formula

a(n) = A102935(n) - 1.

Example

149 is prime, hence 1 is a term.

Mathematica

Select[Range[0, 200], PrimeQ[(130*10^# + 41)/9] &] (* Robert Price, Apr 19 2015 *)

Prog

(PARI) a=19; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-41)
(PARI) for(n=0, 1500, if(isprime((130*10^n+41)/9), print1(n, ", ")))

Crossrefs

Cf. A000533, A002275, A102935.

Sequence in context: A345961 A179203 A371476 * A032916 A044994 A242900

Adjacent sequences: A102014 A102015 A102016 * A102018 A102019 A102020

Keyword

nonn,hard,more

Author

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 28 2004

Extensions

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008

a(18)-a(20) derived from A102935 by Robert Price, Apr 19 2015

Status

approved