Ring

Author

Eric W. Weisstein
March 8, 2005

This notebook downloaded from http://mathworld.wolfram.com/notebooks/Algebra/Ring.nb.

For more information, see Eric's MathWorld entry http://mathworld.wolfram.com/Ring.html.

©2005 Wolfram Research, Inc. except for portions noted otherwise

Counts as a Function of Size

Rings[1]:=1
Rings[n_]:=Module[{f=FactorInteger[n]},
Switch[Evaluate[Sort[f,(Last[#1]<=Last[#2]&)]],
{{2,2}},11,
{{2,3}},52,
{{p_,1}},2,
{{p_,1},{q_,1}},4,
{{p_,2}},11,
{{q_,1},{p_,2}},22,
{{p_,3}},53,
_,0
]
]

Rings/@Range[20]