Search: id:A056245
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%I A056245
%S A056245 0,5,65,1253,8405
%N A056245 Indices of primes in sequence defined by A(0) = 11, A(n) = 10*A(n-1) 
               + 31 for n > 0.
%C A056245 Numbers n such that (130*10^n - 31)/9 is prime.
%C A056245 Numbers n such that digit 1 followed by n >= 0 occurrences of digit 4 
               followed by digit 1 is prime.
%C A056245 Numbers corresponding to terms <= 65 are certified primes. For number 
               corresponding to 1253 see P. De Geest, PDP Reference Table.
%C A056245 a(n) = A082698(n-2) - 2 for n > 1.
%D A056245 Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, 
               MNU 59/8 (2006), pp. 462-467.
%H A056245 P. De Geest, <a href="http://www.worldofnumbers.com/deplat.htm">PDP Reference 
               Table</a>
%H A056245 Makoto Kamada, <a href="http://homepage2.nifty.com/m_kamada/math/14441.htm">
               Factorizations of 144...441</a>.
%e A056245 1444441 is prime, hence 5 is a term.
%o A056245 (PARI) a=11;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a+31)
%o A056245 (PARI) for(n=0,1500,if(isprime((130*10^n-31)/9),print1(n,",")))
%Y A056245 Cf. A000533, A002275, A082698.
%Y A056245 Sequence in context: A103974 A006278 A121822 this_sequence A079482 A147625 
               A157097
%Y A056245 Adjacent sequences: A056242 A056243 A056244 this_sequence A056246 A056247 
               A056248
%K A056245 nonn,hard,more
%O A056245 1,2
%A A056245 Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 18 2000
%E A056245 Additional comments from Klaus Brockhaus (klaus-brockhaus(AT)t-online.de) 
               and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), 
               Dec 28 2004
%E A056245 Edited by N. J. A. Sloane (njas(AT)research.att.com), Jun 15 2007
%E A056245 8405 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008

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