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A101954
Indices of primes in sequence defined by A(0) = 27, A(n) = 10*A(n-1) - 53 for n > 0.
1
35, 182, 329, 392, 17519, 27221
OFFSET
1,1
COMMENTS
Numbers n such that (190*10^n + 53)/9 is prime.
Numbers n such that digit 2 followed by n >= 0 occurrences of digit 1 followed by digit 7 is prime.
Numbers corresponding to terms <= 392 are certified primes.
No further terms up to n=5000. [Harvey P. Dale, Aug 20 2011]
a(7) > 10^5. - Robert Price, Feb 07 2015
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
FORMULA
a(n) = A102949(n) - 1.
EXAMPLE
2111111111111111111111111111111111117 is prime, hence 35 is a term.
MATHEMATICA
a = 27; Flatten[Position[Table[a = 10*a - 53, {n, 500}], _?(PrimeQ[#] &)]]
PROG
(PARI) a=27; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-53)
(PARI) for(n=0, 1500, if(isprime((190*10^n+53)/9), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 23 2004
EXTENSIONS
a(5)-a(6) derived from A102949 by Robert Price, Feb 07 2015
STATUS
approved