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 A101963 Indices of primes in sequence defined by A(0) = 29, A(n) = 10*A(n-1) - 31 for n > 0. 1
 0, 81, 321, 732, 2430, 8385, 15885, 19911 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Numbers n such that (230*10^n + 31)/9 is prime. Numbers n such that digit 2 followed by n >= 0 occurrences of digit 5 followed by digit 9 is prime. Numbers corresponding to terms <= 732 are certified primes. a(9) > 10^5. - Robert Price, Feb 06 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..8. Makoto Kamada, Prime numbers of the form 255...559. Index entries for primes involving repunits. FORMULA a(n) = A102956(n) - 1. EXAMPLE 29 is prime, hence 0 is a term. PROG (PARI) a=29; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-31) (PARI) for(n=0, 1500, if(isprime((230*10^n+31)/9), print1(n, ", "))) CROSSREFS Cf. A000533, A002275, A102956. Sequence in context: A237332 A237325 A158776 * A053171 A237412 A237405 Adjacent sequences: A101960 A101961 A101962 * A101964 A101965 A101966 KEYWORD nonn,hard,more AUTHOR Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 23 2004 EXTENSIONS More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008 a(7)-a(8) derived from A102956 by Robert Price, Feb 06 2015 STATUS approved

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Last modified August 6 23:00 EDT 2024. Contains 375002 sequences. (Running on oeis4.)