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A101568
Indices of primes in sequence defined by A(0) = 53, A(n) = 10*A(n-1) - 27 for n > 0.
1
0, 1, 2, 7, 17, 19, 30, 41, 102, 174, 180, 530, 705, 1076, 1176, 1551, 19736, 32196, 51507, 58274, 62232, 90032
OFFSET
1,3
COMMENTS
Numbers n such that 50*10^n + 3 is prime.
Numbers n such that digit 5 followed by n >= 0 occurrences of digit 0 followed by digit 3 is prime.
Numbers corresponding to terms <= 705 are certified primes.
a(23) > 2*10^5. - Robert Price, Aug 03 2015
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
FORMULA
a(n) = A096254(n) - 1.
EXAMPLE
5003 is prime, hence 2 is a term.
MATHEMATICA
Select[Range[0, 200000], PrimeQ[50*10^# + 3] &] (* Robert Price, Aug 03 2015 *)
PROG
(PARI) a=53; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-27)
(PARI) for(n=0, 1500, if(isprime(50*10^n+3), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 09 2004
EXTENSIONS
1551 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
a(17)-a(22) from Kamada data by Ray Chandler, Apr 30 2015
STATUS
approved