

A101571


Indices of primes in sequence defined by A(0) = 57, A(n) = 10*A(n1)  53 for n > 0.


1




OFFSET

1,1


COMMENTS

Numbers n such that (460*10^n + 53)/9 is prime.
Numbers n such that digit 5 followed by n >= 0 occurrences of digit 1 followed by digit 7 is prime.
Numbers corresponding to terms <= 52 are certified primes. No further terms up to 2400.
a(5) > 10^5.  Robert Price, Jun 20 2015


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..4.
Makoto Kamada, Prime numbers of the form 511...117.
Index entries for primes involving repunits.


FORMULA

a(n) = A103006(n+1)  1.


EXAMPLE

511111111111111111111117 is prime, hence 22 is a term.


PROG

(PARI) a=57; for(n=0, 1000, if(isprime(a), print1(n, ", ")); a=10*a53)
(PARI) for(n=0, 1000, if(isprime((460*10^n+53)/9), print1(n, ", ")))


CROSSREFS

Cf. A000533, A002275, A103006.
Sequence in context: A111576 A277979 A177726 * A290381 A324486 A122502
Adjacent sequences: A101568 A101569 A101570 * A101572 A101573 A101574


KEYWORD

nonn,more


AUTHOR

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwthaachen.de), Dec 09 2004


EXTENSIONS

a(3)a(4) from Kamada data by Ray Chandler, Apr 30 2015


STATUS

approved



