A239142 Number of strict partitions of n having standard deviation sigma > 1.

0, 0, 0, 0, 1, 1, 3, 4, 5, 8, 10, 12, 16, 20, 24, 30, 36, 43, 52, 62, 73, 87, 102, 119, 140, 163, 189, 220, 254, 293, 338, 388, 445, 510, 583, 665, 758, 862, 979, 1111, 1258, 1423, 1608, 1814, 2045, 2302, 2588, 2907, 3262, 3656, 4094, 4580, 5118, 5715, 6376

Offset

1,7

Comments

Regarding standard deviation, see Comments at A238616.

Links

Table of n, a(n) for n=1..55.

Formula

a(n) + A239141(n) = A000009(n) for n >=1.

G.f.: Product_{m>=1} (1+x^m) -1 +(x^5+x^4+x^3+2*x^2+x+1)*x / ((x-1)*(x^2+x+1)). - Alois P. Heinz, Mar 14 2014

Example

The standard deviations of the strict partitions of 9 are 0., 3.5, 2.5, 1.5, 2.16025, 0.5, 1.63299, 0.816497, so that a(9) = 5.

Mathematica

z = 30; g[n_] := Select[IntegerPartitions[n], Max[Length /@ Split@#] == 1 &]; s[t_] := s[t] = Sqrt[Sum[(t[[k]] - Mean[t])^2, {k, 1, Length[t]}]/Length[t]]
Table[Count[g[n], p_ /; s[p] < 1], {n, z}]   (* A239140 *)
Table[Count[g[n], p_ /; s[p] <= 1], {n, z}]  (* A239141 *)
Table[Count[g[n], p_ /; s[p] == 1], {n, z}]  (* periodic 01 *)
Table[Count[g[n], p_ /; s[p] > 1], {n, z}]   (* A239142 *)
Table[Count[g[n], p_ /; s[p] >= 1], {n, z}]  (* A239143 *)
t[n_] := t[n] = N[Table[s[g[n][[k]]], {k, 1, PartitionsQ[n]}]]
ListPlot[Sort[t[30]]] (*plot of st.dev's of strict partitions of 30*)
(* Peter J. C. Moses, Mar 03 2014 *)

Crossrefs

Cf. A239140, A239141, A239142, A000009, A238616.

Sequence in context: A117483 A213513 A344168 * A028288 A118250 A278998

Adjacent sequences: A239139 A239140 A239141 * A239143 A239144 A239145

Keyword

nonn,easy

Author

Clark Kimberling, Mar 11 2014

Status

approved