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A341548
Number of commutative rings with additive group (Z/nZ)^2.
3
1, 6, 6, 28, 6, 36, 6, 79, 35, 36, 6, 168, 6, 36, 36
OFFSET
1,2
COMMENTS
It appears that a(16)=230, but it is preferable to wait for someone to confirm it.
LINKS
B. Fine, Classification of Finite Rings of Order p^2, Mathematics Magazine, 66(4) (1993), 248-252.
C. R. Fletcher, Rings of Small Order, The Mathematical Gazette, 64(427) (1980), 9-22.
Christof Nöbauer, Home page
MATHEMATICA
Clear[phi]; phi[p_, 1] := 6; phi[2, 2] = 28; phi[2, 3] = 79; phi[3, 2] = 35; phi[n_]:= Module[{aux = FactorInteger[n]}, Product[phi[aux[[i, 1]], aux[[i, 2]]], {i, Length[aux]}]];
KEYWORD
nonn,mult,more
AUTHOR
STATUS
approved