A101517 Indices of primes in sequence defined by A(0) = 61, A(n) = 10*A(n-1) - 9 for n > 0.

0, 1, 7, 8, 14, 19, 25, 37, 44, 64, 111, 243, 302, 392, 559, 838, 1008, 1018, 1172, 1333, 2235, 2628, 4425, 8847, 20811, 37743, 72925, 86286

Offset: 1

Author

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 06 2004

Keywords

• nonn
• hard
• more

Comments

Numbers n such that 60*10^n + 1 is prime.

Numbers n such that digit 6 followed by n >= 0 occurrences of digit 0 followed by digit 1 is prime.

Numbers corresponding to terms <= 838 are certified primes.

Certified primality of numbers corresponding to terms 1008,1018,1172,1333 with Primo. - Ryan Propper, Jun 20 2005

Examples

			600000001 is prime, hence 7 is a term.
		

References

• Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.

Links

• Makoto Kamada, Prime numbers of the form 600...001.

Crossrefs

Cf. A000533, A002275, A056805.

Programs

PARI

a=61;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a-9)

PARI

for(n=0,1500,if(isprime(60*10^n+1),print1(n,",")))

Formula

a(n) = A056805(n+1) - 1.

Extensions

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm) and Stefan Steinerberger, Apr 28 2007

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

a(26)-a(28) from Kamada data by Ray Chandler, Apr 23 2015