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A101059
Indices of primes in sequence defined by A(0) = 87, A(n) = 10*A(n-1) - 53 for n > 0.
1
2, 8, 16, 152, 193, 640, 674, 1460, 26428, 48460, 72734
OFFSET
1,1
COMMENTS
Numbers n such that (730*10^n + 53)/9 is prime.
Numbers n such that digit 8 followed by n >= 0 occurrences of digit 1 followed by digit 7 is prime.
Numbers corresponding to terms <= 674 are certified primes.
a(12) > 10^5. - Robert Price, Oct 09 2015
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
FORMULA
a(n) = A103072(n) - 1. - Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
EXAMPLE
8117 is prime, hence 2 is a term.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(730*10^# + 53)/9] &] (* Robert Price, Oct 09 2015 *)
PROG
(PARI) a=87; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-53)
(PARI) for(n=0, 1500, if(isprime((730*10^n+53)/9), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 30 2004
EXTENSIONS
a(9)-a(10) from Kamada data by Ray Chandler, Apr 29 2015
a(11) from Robert Price, Oct 09 2015
STATUS
approved