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%I #19 Jan 17 2019 13:44:08
%S 14,22,36,104,1136,17864,25448
%N Numbers n such that 10^(2n+1)-5*10^n-1 is prime.
%D C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
%H Patrick De Geest, World!Of Numbers, <a href="http://www.worldofnumbers.com/wing.htm#pwp949">Palindromic Wing Primes (PWP's)</a>
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/9/99499.htm#prime">Prime numbers of the form 99...99499...99</a>
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F a(n) = (A077782(n)-1)/2.
%t Do[If[PrimeQ[10^(2n + 1) - 5*10^n - 1], Print[n]], {n, 3000}]
%o (PARI) is(n)=ispseudoprime(10^(2*n+1)-5*10^n-1) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A115073, A183174-A183187.
%K nonn,base
%O 1,1
%A _Ray Chandler_, Dec 28 2010
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