

A101517


Indices of primes in sequence defined by A(0) = 61, A(n) = 10*A(n1)  9 for n > 0.


1



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
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OFFSET

1,3


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


REFERENCES

Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462467.


LINKS

Table of n, a(n) for n=1..28.
Makoto Kamada, Prime numbers of the form 600...001.


FORMULA

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


EXAMPLE

600000001 is prime, hence 7 is a term.


PROG

(PARI) a=61; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a9)
(PARI) for(n=0, 1500, if(isprime(60*10^n+1), print1(n, ", ")))


CROSSREFS

Cf. A000533, A002275, A056805.
Sequence in context: A047274 A037368 A037970 * A015893 A165465 A047521
Adjacent sequences: A101514 A101515 A101516 * A101518 A101519 A101520


KEYWORD

nonn,hard,more


AUTHOR

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


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


STATUS

approved



