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%I #10 Feb 18 2019 06:46:17
%S 63,1023,16383,32767,67108863,1073741823,17179869183,274877906943,
%T 8796093022207,2251799813685247,4611686018427387903,
%U 36893488147419103231
%N Composite numbers of the form 2^k - 1 for which each prime divisor has the form 4j + 3.
%C Needed factorizations are in the Cunningham Project.
%H Amiram Eldar, <a href="/A183076/b183076.txt">Table of n, a(n) for n = 1..39</a>
%H S. S. Wagstaff, Jr., <a href="http://homes.cerias.purdue.edu/~ssw/cun/index.html">The Cunningham Project</a>.
%F a(n) = 2^A183072(n) - 1.
%e 63 = 2^6 - 1 = 3^2 * 7, and 3 and 7 have the form 4j + 3.
%Y Cf. A000668, A136005, A183075, A183077, A183078.
%Y Cf. A000043, A136003, A183071, A183072, A183073, A183074.
%K nonn,hard
%O 1,1
%A _Stuart Clary_, Dec 23 2010
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