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%I #5 Mar 21 2022 11:10:50
%S 1,0,1,1,2,0,1,0,2,0,0,1,0,0,2,2,2,0,0,2,1,0,0,0,5,0,3,1,0,0,0,0,0,0,
%T 2,2,2,0,0,0,2,0,2,0,4,0,2,2,2,0,2,0,0,0,0,0,0,0,2,2,0,0,2,3,0,0,2,2,
%U 0,0,0,0,0,0,5,0,0,0,2,4,5,0,2,1,4,0,0,0,2,0,0,0,0,0,0,0,0,0,0,5,2,0,0,0,2,0,0,3,2,0,2,2,0,0,0,0,0,0
%N a(n) = number of modules with n elements over the ring of integers in the real quadratic field of discriminant 21.
%C See A352550 for comments and PARI code.
%Y Cf. A038540, A038541, A248107, A352550-A352567.
%K nonn
%O 1,5
%A _N. J. A. Sloane_, Mar 20 2022