cp's OEIS Frontend

A056253 Indices of primes in sequence defined by A(0) = 33, A(n) = 10*A(n-1) + 13 for n > 0.

%I A056253 #18 Jan 17 2019 13:44:05
%S A056253 5,11,491,5567,24755
%N A056253 Indices of primes in sequence defined by A(0) = 33, A(n) = 10*A(n-1) + 13 for n > 0.
%C A056253 Numbers n such that (310*10^n - 13)/9 is prime.
%C A056253 Numbers n such that digit 3 followed by n >= 0 occurrences of digit 4 followed by digit 3 is prime.
%C A056253 Numbers corresponding to terms <= 491 are certified primes. For larger numbers see P. De Geest, PDP Reference Table.
%C A056253 a(4) = 5567 is based on A082706.
%D A056253 Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
%H A056253 Patrick De Geest, <a href="http://www.worldofnumbers.com/deplat.htm#pdp343">PDP Reference Table - 343</a>.
%H A056253 Makoto Kamada, <a href="https://stdkmd.net/nrr/3/34443.htm#prime">Prime numbers of the form 344...443</a>.
%H A056253 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F A056253 a(n) = A082706(n) - 2.
%e A056253 3444443 is prime, hence 5 is a term.
%t A056253 Select[Range[0, 2000], PrimeQ[(310 10^# -13) / 9] &] (* _Vincenzo Librandi_, Nov 03 2014 *)
%o A056253 (PARI) a=33;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a+13)
%o A056253 (PARI) for(n=0,1500,if(isprime((310*10^n-13)/9),print1(n,",")))
%Y A056253 Cf. A000533, A002275, A082706.
%K A056253 nonn,hard,more
%O A056253 1,1
%A A056253 _Robert G. Wilson v_, Aug 18 2000
%E A056253 24755 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
%E A056253 Comments section and a link edited by _Patrick De Geest_, Nov 02 2014
%E A056253 Edited by _Ray Chandler_, Nov 05 2014