login
A101133
Indices of primes in sequence defined by A(0) = 71, A(n) = 10*A(n-1) + 11 for n > 0.
1
0, 3, 15, 24, 28, 40, 46, 87, 1131, 1569, 3984, 10608, 12174, 29368
OFFSET
1,2
COMMENTS
Numbers n such that (650*10^n - 11)/9 is prime.
Numbers n such that digit 7 followed by n >= 0 occurrences of digit 2 followed by digit 1 is prime.
Some of the larger entries may only correspond to probable primes.
a(15) > 10^5. - Robert Price, Sep 23 2015
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
FORMULA
a(n) = A103052(n) - 1.
EXAMPLE
72221 is prime, hence 3 is a term.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(650*10^# - 11)/9] &] (* Robert Price, Sep 23 2015 *)
PROG
(PARI) a=71; for(n=0, 1200, if(isprime(a), print1(n, ", ")); a=10*a+11)
(PARI) for(n=0, 1200, if(isprime((650*10^n-11)/9), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 03 2004
EXTENSIONS
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
a(12)-a(14) from Kamada data by Ray Chandler, Apr 29 2015
STATUS
approved