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A101570
Indices of primes in sequence defined by A(0) = 53, A(n) = 10*A(n-1) - 17 for n > 0.
1
0, 2, 18, 108, 128, 279, 386, 446, 486, 1047, 3297, 3459, 9453, 26102, 61692, 66468
OFFSET
1,2
COMMENTS
Numbers n such that (460*10^n + 17)/9 is prime.
Numbers n such that digit 5 followed by n >= 0 occurrences of digit 1 followed by digit 3 is prime.
Numbers corresponding to terms <= 486 are certified primes.
a(17) > 10^5. - Robert Price, Jun 20 2015
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
FORMULA
a(n) = A103005(n) - 1.
EXAMPLE
5113 is prime, hence 2 is a term.
PROG
(PARI) a=53; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-17)
(PARI) for(n=0, 1500, if(isprime((460*10^n+17)/9), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 09 2004
EXTENSIONS
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
a(14) from Kamada data by Ray Chandler, Apr 30 2015
a(15)-a(16) from Robert Price, Jun 20 2015
STATUS
approved