OFFSET
1,2
COMMENTS
An element a of a ring is called a von Neumann regular element if there exists an x such that a = axa.
LINKS
Robert G. Wilson v, Table of n, a(n) for n = 1..41
MATHEMATICA
G[A_, n_] := Reduce[A == A.{{x, y}, {z, t}}.A, Modulus -> n];
H[n_] := Sum[If[G[{{a, b}, {c, d}}, n] === False, 0, 1], {a, n}, {b, n}, {c, n}, {d, n}];
Table[H[n], {n, 2, 14}]
CROSSREFS
KEYWORD
nonn,mult
AUTHOR
José María Grau Ribas, Nov 13 2017
EXTENSIONS
a(19) inserted by José María Grau Ribas, Feb 13 2018
More terms from Robert G. Wilson v, Feb 14 2018
STATUS
approved