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A238619 Number of partitions of n having population standard deviation > 1. 5
0, 0, 0, 0, 1, 2, 5, 8, 15, 22, 33, 47, 68, 93, 132, 176, 239, 314, 412, 536, 693, 884, 1131, 1427, 1803, 2249, 2808, 3489, 4321, 5325, 6552, 8022, 9799, 11913, 14456, 17502, 21136, 25457, 30588, 36673, 43869, 52398, 62437, 74277, 88186, 104526, 123670, 146028 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

COMMENTS

Regarding "standard deviation" see Comments at A238616.

LINKS

Table of n, a(n) for n=1..48.

FORMULA

a(n) + A238617(n) = A000041(n).

EXAMPLE

There are 11 partitions of 6, whose standard deviations are given by these approximations:  0., 2., 1., 1.41421, 0., 0.816497, 0.866025, 0., 0.5, 0.4, 0, so that a(6) = 2.

MAPLE

b:= proc(n, i, m, s, c) `if`(n=0, `if`(s/c-(m/c)^2>1, 1, 0),

      `if`(i=1, b(0$2, m+n, s+n, c+n), add(b(n-i*j, i-1,

       m+i*j, s+i^2*j, c+j), j=0..n/i)))

    end:

a:= n-> b(n$2, 0$3):

seq(a(n), n=1..50);  # Alois P. Heinz, Mar 11 2014

MATHEMATICA

z = 55; g[n_] := g[n] = IntegerPartitions[n]; 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}]   (*A238616*)

Table[Count[g[n], p_ /; s[p] <= 1], {n, z}]  (*A238617*)

Table[Count[g[n], p_ /; s[p] == 1], {n, z}]  (*A238618*)

Table[Count[g[n], p_ /; s[p] > 1], {n, z}]   (*A238619*)

Table[Count[g[n], p_ /; s[p] >= 1], {n, z}]  (*A238620*)

t[n_] := t[n] = N[Table[s[g[n][[k]]], {k, 1, PartitionsP[n]}]]

ListPlot[Sort[t[30]]] (*plot of st.dev's of partitions of 30*)

(* Second program: *)

b[n_, i_, m_, s_, c_] := b[n, i, m, s, c] = If[n == 0,

     If[s/c - (m/c)^2 > 1, 1, 0], If[i == 1, b[0, 0, m+n, s+n, c+n],

     Sum[b[n - i*j, i - 1, m + i*j, s + i^2*j, c+j], {j, 0, n/i}]]];

a[n_] := b[n, n, 0, 0, 0];

Array[a, 50] (* Jean-François Alcover, Jun 03 2021, after Alois P. Heinz *)

CROSSREFS

Cf. A238616.

Sequence in context: A183409 A262867 A024808 * A323285 A077866 A098894

Adjacent sequences:  A238616 A238617 A238618 * A238620 A238621 A238622

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling, Mar 01 2014

STATUS

approved

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Last modified August 1 14:14 EDT 2021. Contains 346391 sequences. (Running on oeis4.)