%I A016090
%S A016090 6,76,376,9376,9376,109376,7109376,87109376,787109376,1787109376,
%T A016090 81787109376,81787109376,81787109376,40081787109376,740081787109376,
%U A016090 3740081787109376,43740081787109376,743740081787109376
%N A016090 Automorphic numbers ending in digit 6.
%C A016090 Also called congruent numbers.
%C A016090 a(n)^2 == a(n) (mod 10^n), that is, a(n) is idempotent of Z[10^n].
%D A016090 R. Cuculiere, Jeux Mathematiques, in Pour la Science, No. 6 (1986), 10-15.
%D A016090 V. deGuerre and R. A. Fairbairn, Automorphic numbers, J. Rec. Math., 
               1 (No. 3, 1968), 173-179.
%D A016090 R. A. Fairbairn, More on automorphic numbers, J. Rec. Math., 2 (No. 3, 
               1969), 170-174.
%D A016090 Jan Gullberg, Mathematics, From the Birth of Numbers, W. W. Norton & 
               Co., NY, page 253-4.
%D A016090 Ya. I. Perelman, Algebra can be fun, pp. 97-98.
%D A016090 A. M. Robert, A Course in p-adic Analysis, Springer, 2000; see pp. 63, 
               419.
%D A016090 C. P. Schut, Idempotents. Report AM-R9101, Centrum voor Wiskunde en Informatica, 
               Amsterdam, 1991.
%D A016090 Xiaolong Ron Yu, Curious Numbers, Pi Mu Epsilon Journal, Spring 1999, 
               pp. 819-823.
%H A016090 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               AutomorphicNumber.html">Link to a section of The World of Mathematics.</
               a>
%H A016090 <a href="Sindx_Ar.html#automorphic">Index entries for sequences related 
               to automorphic numbers</a>
%F A016090 a(n) = 16^(5^n) mod 10^n.
%e A016090 a(5) = 09376 because 09376^2 == 87909376 ends in 09376.
%Y A016090 A018248 gives associated 10-adic number.
%Y A016090 A003226 = {0, 1} union A007185 union (this sequence).
%Y A016090 Sequence in context: A162863 A126462 A081066 this_sequence A137132 A053337 
               A155643
%Y A016090 Adjacent sequences: A016087 A016088 A016089 this_sequence A016091 A016092 
               A016093
%K A016090 nonn,base
%O A016090 1,1
%A A016090 Robert G. Wilson v (rgwv(AT)rgwv.com), Dave Wilson (davidwwilson(AT)comcast.net)
%E A016090 Edited by David W. Wilson, Sep 26, 2002