%I A006045 M3946
%S A006045 1,26,272,722,5270,5260,37358
%N A006045 Sum of orders of all 2 X 2 matrices with entries mod n.
%C A006045 The order of a matrix M over Z/(nZ) is the smallest k such that M^k is 
               idempotent.
%D A006045 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A006045 Wilansky, Albert; Spectral decomposition of matrices for high school 
               students. Math. Mag. 41 1968 51-59.
%Y A006045 Sequence in context: A059744 A016106 A092723 this_sequence A137787 A022686 
               A130901
%Y A006045 Adjacent sequences: A006042 A006043 A006044 this_sequence A006046 A006047 
               A006048
%K A006045 nonn
%O A006045 1,2
%A A006045 N. J. A. Sloane (njas(AT)research.att.com), Albert Wilansky
%E A006045 The article gives an incorrect value for a(5).