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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 (list; graph; refs; listen; history; text; internal format)
 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. LINKS Makoto Kamada, Factorizations of 211...117. 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 Cf. A000533, A002275, A102949. Sequence in context: A219825 A194716 A220047 * A220201 A005937 A341043 Adjacent sequences:  A101951 A101952 A101953 * A101955 A101956 A101957 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

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Last modified July 6 14:10 EDT 2022. Contains 355110 sequences. (Running on oeis4.)