

A101737


Indices of primes in sequence defined by A(0) = 49, A(n) = 10*A(n1)  1 for n > 0.


1



2, 3, 5, 9, 11, 17, 39, 47, 95, 105, 113, 143, 363, 617, 1089, 11369, 59453, 196683
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OFFSET

1,1


COMMENTS

Numbers n such that (440*10^n + 1)/9 is prime.
Numbers n such that digit 4 followed by n >= 0 occurrences of digit 8 followed by digit 9 is prime.
Numbers corresponding to terms <= 617 are certified primes.
a(19) > 2*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..18.
Makoto Kamada, Prime numbers of the form 488...889.
Index entries for primes involving repunits.


FORMULA

a(n) = A103000(n+1)  1.


EXAMPLE

4889 is prime, hence 2 is a term.


MATHEMATICA

Select[Range[0, 10000], PrimeQ[(440*10^# + 1)/9] &]


PROG

(PARI) a=49; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a1)
(PARI) for(n=0, 1500, if(isprime((440*10^n+1)/9), print1(n, ", ")))


CROSSREFS

Cf. A000533, A002275, A103000.
Sequence in context: A238657 A329327 A329357 * A176550 A293036 A214125
Adjacent sequences: A101734 A101735 A101736 * A101738 A101739 A101740


KEYWORD

nonn,hard,more


AUTHOR

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwthaachen.de), Dec 14 2004


EXTENSIONS

a(16)a(18) derived from A103000 by Robert Price, Mar 30 2015


STATUS

approved



