A179389 - OEIS

%I #4 Mar 30 2012 17:31:29

%S 0,1,2,6,55,360,3035,20502,160077,1369317

%N The number of sorted length n integer sequences with mean zero and sample standard deviation n.

%t Clear[f, g, a, n, s, ss]; f[0, 0, 0] := {{}}; f[0, s_, ss_] := {}; f[n_, s_, ss_] := f[n, s, ss] = Union[ Sort /@ Apply[Join, Table[Map[Append[ #, i] &, f[n - 1, s - i, ss - i^2]], {i, -Floor[Sqrt[ss]], Floor[Sqrt[ss]]}]]]; g[n_, s_] := f[n, 0, s^2 (n - 1)]; a[n_] := Length[g[n, n]]; Table[a[n], {n, 2, 7}]

%K nonn,more

%O 2,3

%A Todd Will (will.todd(AT)uwlax.edu), Jul 12 2010

%E a(10) & a(11) from _Robert G. Wilson v_, Jul 24 2010