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Numbers k such that (14*10^(k-1) - 41)/9 is a plateau prime.
2

%I #22 Nov 09 2019 03:14:03

%S 3,5,21,33,401,563,7017,37685

%N Numbers k such that (14*10^(k-1) - 41)/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#pdp151">PDP Reference Table - 151</a>.

%H Makoto Kamada, <a href="https://stdkmd.net/nrr/1/15551.htm#prime">Prime numbers of the form 155...551</a>.

%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.

%F a(n) = A056246(n+1) + 2.

%e k=21 -> (14*10^(21-1) - 41)/9 = 155555555555555555551.

%Y Cf. A056246, A068646, A082697-A082720.

%K nonn,base,more

%O 1,1

%A _Patrick De Geest_, Apr 13 2003

%E 37685 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008

%E Edited by _Ray Chandler_, Nov 04 2014