The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A101519 Indices of primes in sequence defined by A(0) = 63, A(n) = 10*A(n-1) - 17 for n > 0. 1
 1, 2, 4, 10, 11, 22, 74, 100, 121, 172, 646, 2014, 2683, 11699, 19624 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Numbers n such that (550*10^n + 17)/9 is prime. Numbers n such that digit 6 followed by n >= 0 occurrences of digit 1 followed by digit 3 is prime. Numbers corresponding to terms <= 646 are certified primes. a(16) > 10^5 - Robert Price, Sep 09 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 611...113. FORMULA a(n) = A103027(n) - 1. EXAMPLE 611113 is prime, hence 4 is a term. MATHEMATICA Select[Range[0, 100000], PrimeQ[(550*10^# + 17)/9] &] (* Robert Price, Sep 09 2015 *) PROG (PARI) a=63; for(n=0, 1000, if(isprime(a), print1(n, ", ")); a=10*a-17) (PARI) for(n=0, 1000, if(isprime((550*10^n+17)/9), print1(n, ", "))) (MAGMA) [n: n in [0..500]| IsPrime((550*10^n + 17) div 9)]; // Vincenzo Librandi, Sep 10 2015 CROSSREFS Cf. A000533, A002275, A103027. Sequence in context: A136818 A293556 A029984 * A227204 A249446 A184815 Adjacent sequences:  A101516 A101517 A101518 * A101520 A101521 A101522 KEYWORD nonn,hard,more AUTHOR Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 06 2004 EXTENSIONS More terms from Stefan Steinerberger, May 06 2007 a(14)-a(15) from Kamada data by Ray Chandler, Apr 30 2015 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 22 07:34 EDT 2020. Contains 337289 sequences. (Running on oeis4.)