%I #20 Nov 09 2019 04:16:59
%S 3,5,9,41,87,201,731,1461,23673,28631
%N Numbers k such that (18*10^(k-1) - 81)/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#pdp191">PDP Reference Table - 191</a>.
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/1/19991.htm#prime">Prime numbers of the form 199...991</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F a(n) = A056250(n+1) + 2.
%e k=9 -> (18*10^(9-1) - 81)/9 = 199999991.
%Y Cf. A082697-A082720, A056250, A068649.
%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
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