A101396 -id:A101396 - cp's OEIS frontend

A101848 Indices of primes in sequence defined by A(0) = 31, A(n) = 10*A(n-1) + 81 for n > 0.

0, 16, 18, 28, 42, 118, 172, 948, 1608, 5578, 19678, 34146, 43492, 97798

Offset: 1

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

Numbers n such that (360*10^n - 81)/9 is prime.
Numbers n such that digit 3 followed by n >= 0 occurrences of digit 9 followed by digit 1 is prime.
Numbers corresponding to terms <= 948 are certified primes.
a(15) > 10^5. - Robert Price, Mar 17 2015

			31 is prime, hence 0 is a term.

Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.

Makoto Kamada, Prime numbers of the form 399...991.
Index entries for primes involving repunits.

Cf. A000533, A002275, A101396.

Select[Range[0, 1000], PrimeQ[(360*10^# - 81)/9] &] (* Robert Price, Mar 17 2015 *)

a=31;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a+81)

for(n=0,1500,if(isprime((360*10^n-81)/9),print1(n,",")))

a(n) = A101396(n) - 1.

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008

a(12)-a(14) derived from A101396 by Robert Price, Mar 17 2015

cp's OEIS Frontend

A101848 Indices of primes in sequence defined by A(0) = 31, A(n) = 10*A(n-1) + 81 for n > 0.

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