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 A101010 Indices of primes in sequence defined by A(0) = 93, A(n) = 10*A(n-1) + 23 for n > 0. 1
 1, 19, 103, 328, 1441, 1720, 24886 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Numbers n such that (860*10^n - 23)/9 is prime. Numbers n such that digit 9 followed by n >= 0 occurrences of digit 5 followed by digit 3 is prime. Numbers corresponding to terms <= 328 are certified primes. a(8) > 10^5. - Robert Price, Nov 08 2015 REFERENCES Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467. LINKS Makoto Kamada, Prime numbers of the form 955...553. FORMULA a(n) = A103101(n+1) - 1. EXAMPLE 953 is prime, hence 1 is a term. MATHEMATICA Select[Range[0, 100000], PrimeQ[(860*10^# - 23)/9] &] (* Robert Price, Nov 08 2015 *) PROG (PARI) a=93; for(n=0, 2000, if(isprime(a), print1(n, ", ")); a=10*a+23) (PARI) for(n=0, 2000, if(isprime((860*10^n-23)/9), print1(n, ", "))) CROSSREFS Cf. A000533, A002275, A103101. Sequence in context: A054658 A023296 A139948 * A201854 A195460 A195461 Adjacent sequences:  A101007 A101008 A101009 * A101011 A101012 A101013 KEYWORD nonn,hard,more AUTHOR Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 27 2004 EXTENSIONS a(7) from Kamada data by Ray Chandler, Apr 28 2015 STATUS approved

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Last modified May 24 05:29 EDT 2022. Contains 354005 sequences. (Running on oeis4.)