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Numbers of the form n=12s+7, where q=4s+3 is a prime for which the order of 2 is either q-1 or (q-1)/2.
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%I #5 Jun 23 2014 16:31:12

%S 7,19,31,55,67,139,175,199,211,235,247,307,319,391,415,487,499,535,

%T 571,595,631,679,715,787,811,931,1039,1075,1099,1135,1147,1255,1327,

%U 1387,1399,1435,1459,1471,1507,1567,1639,1687,1759,1795,1819,1855

%N Numbers of the form n=12s+7, where q=4s+3 is a prime for which the order of 2 is either q-1 or (q-1)/2.

%D L. Heffter, Über das Problem der Nachbargebiete, Math. Ann., 38 (1891) 477-508.

%D G. Ringel, Map Color Theorem, Springer, 1974, p. 6.

%Y Equals 3*A105876(n) - 2.

%K nonn

%O 1,1

%A _R. K. Guy_, Feb 11 2006