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%I #37 Oct 30 2023 18:05:23
%S 3,7,15,23,27,35,59,63,67,155,1867,3111,23517,235415
%N Numbers k such that (10^k - 1)/3 + 4*10^floor(k/2) is a palindromic wing prime (a.k.a. near-repdigit palindromic prime).
%C Prime versus probable prime status and proofs are given in the author's table.
%C a(14) > 200000. - _Robert Price_, Dec 29 2016
%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#pwp373">Palindromic Wing Primes (PWP's)</a>
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/3/33733.htm#prime">Prime numbers of the form 33...33733...33</a>
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F a(n) = 2*A183176(n) + 1.
%e 23 is a term because (10^23 - 1)/3 + 4*10^11 = 33333333333733333333333.
%t Do[ If[ PrimeQ[(10^n + 12*10^Floor[n/2] - 1)/3], Print[n]], {n, 3, 23600, 2}] (* _Robert G. Wilson v_, Dec 16 2005 *)
%Y Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A115073, A183174-A183187.
%K more,nonn,base
%O 1,1
%A _Patrick De Geest_, Nov 16 2002
%E Name corrected by _Jon E. Schoenfield_, Oct 31 2018
%E a(14) from _Robert Price_, Oct 30 2023
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