%I #28 Nov 09 2019 03:13:48
%S 5,13,17,19,37,53,73,101,6233,24029,40223,66395
%N Numbers k such that (15*10^(k-1) - 51)/9 is a plateau prime.
%C Prime versus probable prime status and proofs are given in the author's table.
%D C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
%H Patrick De Geest, <a href="http://www.worldofnumbers.com/deplat.htm#pdp161">PDP Reference Table - 161</a>.
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/1/16661.htm#prime">Prime numbers of the form 166...661</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F a(n) = A056247(n+1) + 2.
%e k=13 -> (15*10^(13-1) - 51)/9 = 1666666666661.
%o (PARI) is(n)=ispseudoprime(2*(10^n-1)/3-5*(10^(n-1)+1)) || ispseudoprime(15*10^(n-1)-51)/9 \\ _Charles R Greathouse IV_, Feb 07 2013
%Y Cf. A056247, A068647, A082697-A082720.
%K nonn,base,more
%O 1,1
%A _Patrick De Geest_, Apr 13 2003
%E More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
%E Edited by _Ray Chandler_, Nov 04 2014