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 A100999 Indices of primes in sequence defined by A(0) = 97, A(n) = 10*A(n-1) - 53 for n > 0. 1
 0, 16, 22, 72, 130, 472, 684, 700, 1908, 3028, 3472, 4192, 9930 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Numbers n such that (820*10^n + 53)/9 is prime. Numbers n such that digit 9 followed by n >= 0 occurrences of digit 1 followed by digit 7 is prime. Numbers corresponding to terms <= 700 are certified primes. a(14) > 10^5. - Robert Price, Oct 25 2015 REFERENCES Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467. LINKS Table of n, a(n) for n=1..13. Makoto Kamada, Prime numbers of the form 911...117. Index entries for primes involving repunits. FORMULA a(n) = A100473(n) - 1. EXAMPLE 911111111111111117 is prime, hence 16 is a term. MATHEMATICA Select[Range[0, 100000], PrimeQ[(820*10^# + 53)/9] &] (* Robert Price, Oct 25 2015 *) PROG (PARI) a=97; for(n=0, 1000, if(isprime(a), print1(n, ", ")); a=10*a-53) (PARI) for(n=0, 1000, if(isprime((820*10^n+53)/9), print1(n, ", "))) CROSSREFS Cf. A000533, A002275, A100473. Sequence in context: A305337 A322344 A316417 * A304923 A306163 A317380 Adjacent sequences: A100996 A100997 A100998 * A101000 A101001 A101002 KEYWORD nonn,hard,more AUTHOR Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 27 2004 EXTENSIONS More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008 STATUS approved

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Last modified July 21 09:16 EDT 2024. Contains 374472 sequences. (Running on oeis4.)