

A101002


Indices of primes in sequence defined by A(0) = 93, A(n) = 10*A(n1)  7 for n > 0.


1



4, 28, 59, 146, 185, 455, 677, 1372, 3377, 15725, 68230
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OFFSET

1,1


COMMENTS

Numbers n such that (830*10^n + 7)/9 is prime.
Numbers n such that digit 9 followed by n >= 0 occurrences of digit 2 followed by digit 3 is prime.
Numbers corresponding to terms <= 677 are certified primes.
a(12) > 10^5.  Robert Price, Oct 31 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..11.
Makoto Kamada, Prime numbers of the form 922...223.
Index entries for primes involving repunits.


FORMULA

a(n) = A103094(n)  1.


EXAMPLE

922223 is prime, hence 4 is a term.


MATHEMATICA

Select[Range[0, 300], PrimeQ[(830*10^# + 7)/9] &] (* Robert Price, Oct 31 2015 *)


PROG

(PARI) a=93; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a7)
(PARI) for(n=0, 1500, if(isprime((830*10^n+7)/9 ), print1(n, ", ")))


CROSSREFS

Cf. A000533, A002275, A103094.
Sequence in context: A069518 A151912 A307135 * A197542 A203280 A085024
Adjacent sequences: A100999 A101000 A101001 * A101003 A101004 A101005


KEYWORD

nonn,hard,more,less


AUTHOR

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwthaachen.de), Nov 27 2004


EXTENSIONS

One more term from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
a(10) from Kamada data by Ray Chandler, Apr 28 2015
a(11) from Robert Price, Oct 31 2015


STATUS

approved



