

A101846


Indices of primes in sequence defined by A(0) = 37, A(n) = 10*A(n1) + 17 for n > 0.


1




OFFSET

1,2


COMMENTS

Numbers n such that (350*10^n  17)/9 is prime.
Numbers n such that digit 3 followed by n >= 0 occurrences of digit 8 followed by digit 7 is prime.
a(5) > 10^5.  Robert Price, Mar 30 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 388...887.
Index entries for primes involving repunits.


FORMULA

a(n) = A102979(n+1)  1.


EXAMPLE

3888887 is prime, hence 5 is a term.


MATHEMATICA

Select[Range[0, 100], PrimeQ[(350*10^#  17)/9] &]


PROG

(PARI) a=37; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+17)
(PARI) for(n=0, 1500, if(isprime((350*10^n17)/9), print1(n, ", ")))


CROSSREFS

Cf. A000533, A002275, A102979.
Sequence in context: A022918 A212617 A160741 * A292742 A260262 A058051
Adjacent sequences: A101843 A101844 A101845 * A101847 A101848 A101849


KEYWORD

nonn,hard,more


AUTHOR

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwthaachen.de), Dec 20 2004


EXTENSIONS

a(3)a(4) derived from A102979 by Robert Price, Mar 30 2015


STATUS

approved



