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%I #22 Nov 10 2019 01:33:34
%S 11,31,121,485,1487,1579,13673,13811,15095,72773,94212
%N Numbers k such that (67*10^(k-1) + 23)/9 is a depression 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#pdp747">PDP Reference Table - 747</a>.
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/7/74447.htm#prime">Prime numbers of the form 744...447</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F a(n) = A056258(n) + 2.
%e k=11 -> (67*10^(11-1) + 23)/9 = 74444444447.
%Y Cf. A082697-A082720, A056258.
%K nonn,base,hard,more
%O 1,1
%A _Patrick De Geest_, Apr 13 2003
%E a(10)=72773 from _Ray Chandler_, Nov 16 2010
%E a(11)=94212 from _Ray Chandler_, Feb 21 2011
%E Edited by _Ray Chandler_, Nov 05 2014
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