|
%I
%S 0,2,3,7,13,15,23,60,79,86,103,107,143,2156,3324,4121
%N Indices of primes in sequence defined by A(0) = 43, A(n) = 10*A(n-1) + 63 for n > 0.
%C Numbers n such that (450*10^n - 63)/9 is prime.
%C Numbers n such that digit 4 followed by n >= 0 occurrences of digit 9 followed by digit 3 is prime.
%C Numbers corresponding to terms <= 143 are certified primes.
%D Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
%H Makoto Kamada, <a href="http://homepage2.nifty.com/m_kamada/math/factorizations.htm">Factorizations of near-repdigit numbers</a>.
%e 4993 is prime, hence 2 is a term.
%o (PARI) a=43;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a+63)
%o (PARI) for(n=0,1500,if(isprime((450*10^n-63)/9),print1(n,",")))
%Y Cf. A000533, A002275.
%Y a(n) = A103002(n) - 1.
%K nonn,hard,more
%O 1,2
%A _Klaus Brockhaus_ and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 14 2004
%E More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
|
