Search: id:A077775
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%I A077775
%S A077775 3,7,15,123,181,185,539,597,643,743,1553,3135,4769,5133,6177,11733,
%T A077775 16103,18997,25271,49025
%N A077775 Palindromic wing primes (a.k.a. near-repdigit palindromes) of the form 
               (10^a(n)-1)/3-2*10^[ a(n)/2 ].
%C A077775 Prime versus probable prime status and proofs are given in the author's 
               table.
%D A077775 C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 
               28, No. 1, 1996-97, pp. 1-9.
%H A077775 Patrick De Geest, World!Of Numbers, <a href="http://www.worldofnumbers.com/
               wing.htm#pwp313">Palindromic Wing Primes (PWP's)</a>
%H A077775 Makoto Kamada, <a href="http://homepage2.nifty.com/m_kamada/math/33133.htm">
               Factorizations of 33...33133...33</a>
%e A077775 a(n)=15 -> (10^15-1)/3-2*10^7 = 333333313333333.
%t A077775 Do[ If[ PrimeQ[(10^n - 6*10^Floor[n/2] - 1)/3], Print[n]], {n, 3, 49100, 
               2}] (from Robert G. Wilson v (rgwv(at)rgwv.com), Dec 16 2005)
%Y A077775 Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A114633-A114647.
%Y A077775 Sequence in context: A023370 A096422 A154795 this_sequence A033089 A153578 
               A018852
%Y A077775 Adjacent sequences: A077772 A077773 A077774 this_sequence A077776 A077777 
               A077778
%K A077775 nonn,base
%O A077775 1,1
%A A077775 Patrick De Geest (pdg(AT)worldofnumbers.com), Nov 16 2002.

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