A101846 Indices of primes in sequence defined by A(0) = 37, A(n) = 10*A(n-1) + 17 for n > 0.

0, 5, 10175, 56897

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. 462-467.

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^n-17)/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.rwth-aachen.de), Dec 20 2004

Extensions

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

Status

approved