%I A077786
%S A077786 177,225,397,1245,8457,20105
%N A077786 Palindromic wing primes (a.k.a. near-repdigit palindromes) of the form 
               (10^a(n)-1)-4*10^[ a(n)/2 ].
%C A077786 Prime versus probable prime status and proofs are given in the author's 
               table.
%D A077786 C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 
               28, No. 1, 1996-97, pp. 1-9.
%H A077786 Patrick De Geest, World!Of Numbers, <a href="http://www.worldofnumbers.com/
               wing.htm#pwp959">Palindromic Wing Primes (PWP's)</a>
%H A077786 Makoto Kamada, <a href="http://homepage2.nifty.com/m_kamada/math/99599.htm">
               Factorizations of 99...99599...99</a>
%e A077786 a(n)=177 -> (10^177-1)-4*10^88 = 99...99599...99.
%t A077786 Do[ If[ PrimeQ[10^n - 4*10^Floor[n/2] - 1], Print[n]], {n, 3, 20200, 
               2}] (from Robert G. Wilson v (rgwv(at)rgwv.com), Dec 16 2005)
%Y A077786 Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A114633-A114647.
%Y A077786 Sequence in context: A159442 A046189 A164843 this_sequence A147028 A105988 
               A083620
%Y A077786 Adjacent sequences: A077783 A077784 A077785 this_sequence A077787 A077788 
               A077789
%K A077786 nonn,base
%O A077786 1,1
%A A077786 Patrick De Geest (pdg(AT)worldofnumbers.com), Nov 16 2002.