cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-7 of 7 results.

A238640 Position of [n, n, ..., n] (n n's) in Mathematica-ordered list of partitions of n^2.

Original entry on oeis.org

1, 1, 3, 19, 168, 1582, 15546, 157051, 1625368, 17159223, 184277224, 2008388660, 22172275440, 247558926150, 2791793968821, 31764451979736, 364283594455091, 4207485803818522, 48908343969469479, 571811846280602486, 6720473048598172508, 79363083519870386700
Offset: 0

Views

Author

Clark Kimberling, Mar 04 2014

Keywords

Examples

			The partitions of 4 in Mathematica order are 4, 31, 22, 211, 1111.  The position of 22 is a(2) = 3.
		

Crossrefs

Cf. A000290, A072213, A080577 (Mathematica ordering), A238638, A238639, A330661, A332706.

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(n=0, 1,
          `if`(i<1, 0, b(n, i-1) +`if`(i>n, 0, b(n-i, i))))
        end:
    a:= n-> 1 +add(b(n^2-j, j), j=n+1..n^2):
    seq(a(n), n=0..20);  # Alois P. Heinz, Sep 03 2014
  • Mathematica
    r[n_] := Table[n, {k, 1, n}]; Flatten[Table[Position[IntegerPartitions[n^2], r[n]], {n, 0, 8}]]
    b[n_, i_] := b[n, i] = If[n==0, 1, If[i<1, 0, b[n, i-1]+If[i>n, 0, b[n-i, i]]]]; a[n_] := 1+Sum[b[n^2-j, j], {j, n+1, n^2}]; Table[a[n], {n, 0, 20}] (* Jean-François Alcover, Oct 28 2015, after Alois P. Heinz *)

Extensions

a(9)-a(21) from Alois P. Heinz, Sep 03 2014

A332706 Index position of {2}^n within the list of partitions of 2n in canonical ordering.

Original entry on oeis.org

1, 1, 3, 8, 18, 37, 71, 128, 223, 376, 617, 991, 1563, 2423, 3704, 5589, 8333, 12293, 17959, 25996, 37318, 53153, 75153, 105535, 147249, 204201, 281563, 386128, 526795, 715191, 966437, 1300125, 1741598, 2323487, 3087701, 4087933, 5392747, 7089463, 9289053
Offset: 0

Views

Author

Alois P. Heinz, Feb 20 2020

Keywords

Comments

The canonical ordering of partitions is described in A080577.

Examples

			a(3) = 8, because 222 has position 8 within the list of partitions of 6 in canonical ordering: 6, 51, 42, 411, 33, 321, 3111, 222, ... .
		

Crossrefs

Bisection (even part) of A058984.

Programs

  • Maple
    a:= n-> combinat[numbpart](2*n)-n:
    seq(a(n), n=0..44);
  • Mathematica
    a[n_] := PartitionsP[2n] - n;
    Table[a[n], {n, 0, 44}] (* Jean-François Alcover, Aug 20 2021, from Maple *)

Formula

a(n) = A000041(2n) - n.
a(n) = A058984(2n).
a(n) = A330661(2n,n).

A238639 Position of [n, n-1, ..., 2, 1] in Mathematica-ordered list of partitions of n(n+1)/2.

Original entry on oeis.org

1, 1, 2, 6, 23, 103, 498, 2493, 12741, 66224, 348963, 1859009, 9994196, 54155387, 295477841, 1621962199, 8951635343, 49644856801, 276540258555, 1546630084062, 8681889729354, 48900895532763, 276302483274825, 1565747892473958, 8896975706929141, 50683901455201860
Offset: 0

Views

Author

Clark Kimberling, Mar 04 2014

Keywords

Examples

			The partitions of 6 in Mathematica order are 6, 51, 42, 411, 33, 321, 3111, 222, 2211, 21111, 111111.  The position of 321 is a(3) = 6.
		

Crossrefs

Cf. A000217, A080577 (Mathematica ordering), A238638, A238640, A330661, A332706.

Programs

  • Maple
    g:= (n, i)-> `if`(n=0, 1, g(n-i+1, i-1)+ b(n-i, i)):
    b:= proc(n, i) option remember; `if`(n=0, 1,
         `if`(i<1, 0, b(n, i-1)+`if`(i>n, 0, b(n-i, i))))
        end:
    a:= n-> (m-> add(b(m-j, min(j, m-j)), j=n+1..m)+
                     g(m-n, n))(n*(n+1)/2):
    seq(a(n), n=0..25);  # Alois P. Heinz, Jun 03 2015
  • Mathematica
    r[n_] := Table[n - k, {k, 0, n - 1}]; Flatten[Table[Position[IntegerPartitions[n (n + 1)/2], r[n]], {n, 0, 2}]]
    g[n_, i_] := If[n==0, 1, g[n-i+1, i-1] + b[n-i, i]]; b[n_, i_] := b[n, i] = If[n==0, 1, If[i<1, 0, b[n, i-1] + If[i>n, 0, b[n-i, i]]]]; a[n_] := Function[m, Sum[b[m-j, Min[j, m-j]], {j, n+1, m}] + g[m-n, n]][n(n+1)/2]; Table[a[n], {n, 0, 25}] (* Jean-François Alcover, Oct 28 2015, after Alois P. Heinz *)

Extensions

a(13)-a(17) from Manfred Scheucher, Jun 01 2015
a(18)-a(25) from Alois P. Heinz, Jun 02 2015

A216053 a(n) is the position of the last two-tuple within the reverse lexicographic set of partitions of 2n and 2n+1, with a(1)-a(n) representing the positions of every 2-tuple partition of 2n and 2n+1.

Original entry on oeis.org

2, 3, 5, 8, 13, 20, 31, 46, 68, 98, 140, 196, 273, 374, 509, 685, 916, 1213, 1598, 2088, 2715, 3507, 4509, 5764, 7339, 9297, 11733, 14743, 18461, 23026, 28630, 35472, 43821, 53964, 66274, 81157, 99134, 120771, 146786, 177971, 215309, 259892, 313066, 376327
Offset: 1

Views

Author

J. Stauduhar, Oct 12 2012

Keywords

Examples

			With n = 3, 2n = 6.  The partitions of 6 are {{6}, {5,1}, {4,2}, {4,1,1}, {3,3}, {3,2,1}, {3,1,1,1}, {2,2,2}, {2,2,1,1}, {2,1,1,1,1}, {1,1,1,1,1,1}}.  The last 2-tuple is located at position 5. The positions of all 2-tuples are 2, 3, and 5.
		

Crossrefs

A diagonal of A181187.

Programs

  • Mathematica
    RecurrenceTable[{a[n+1] == a[n] + PartitionsP[(n)], a[1] == 2}, a, {n, 1, 44}]

Formula

a(n) ~ exp(Pi*sqrt(2*n/3)) / (Pi*2^(3/2)*sqrt(n)). - Vaclav Kotesovec, May 24 2018
a(n) = A330661(2n,2) = A330661(2n+1,2). - Alois P. Heinz, Feb 20 2020

A332719 Index position of {n}^3 within the list of partitions of 3n in canonical ordering.

Original entry on oeis.org

1, 3, 8, 19, 44, 93, 187, 357, 657, 1166, 2015, 3393, 5594, 9044, 14378, 22501, 34734, 52931, 79735, 118823, 175337, 256347, 371606, 534377, 762721, 1080979, 1521925, 2129330, 2961580, 4096006, 5634855, 7712558, 10505457, 14243772, 19227383, 25845241, 34600673
Offset: 0

Views

Author

Alois P. Heinz, Feb 20 2020

Keywords

Comments

The canonical ordering of partitions is described in A080577.

Examples

			a(2) = 8, because 222 has position 8 within the list of partitions of 6 in canonical ordering: 6, 51, 42, 411, 33, 321, 3111, 222, ... .
		

Crossrefs

Programs

  • Maple
    b:= proc(n, i) option remember;
         `if`(n=0, 1, b(n-i, i)+g(n, i-1))
        end:
    g:= proc(n, i) option remember; `if`(n=0 or i=1, 1,
         `if`(i<1, 0, g(n-i, min(n-i, i))+g(n, i-1)))
        end:
    a:= n-> g(3*n$2)-b(3*n, n)+1:
    seq(a(n), n=0..37);
  • Mathematica
    b[n_, i_] := b[n, i] = If[n == 0, 1, b[n - i, i] + g[n, i - 1]];
    g[n_, i_] := g[n, i] = If[n == 0 || i == 1, 1, If[i < 1, 0, g[n - i, Min[n - i, i]] + g[n, i - 1]]];
    a[n_] := g[3n, 3n] - b[3n, n] + 1;
    a /@ Range[0, 37] (* Jean-François Alcover, Jan 06 2021, after Alois P. Heinz *)

Formula

a(n) ~ exp(2*Pi*sqrt(n/3)) / (4*Pi*sqrt(n)). - Vaclav Kotesovec, Feb 28 2020

A332720 Index position of {3}^n within the list of partitions of 3n in canonical ordering.

Original entry on oeis.org

1, 1, 5, 19, 59, 150, 349, 745, 1515, 2936, 5514, 10036, 17851, 31039, 53006, 88943, 147057, 239701, 385885, 613855, 966137, 1505137, 2323124, 3553914, 5392315, 8117758, 12131618, 18003740, 26543030, 38886999, 56633453, 82009410, 118113488, 169229009, 241264461
Offset: 0

Views

Author

Alois P. Heinz, Feb 20 2020

Keywords

Comments

The canonical ordering of partitions is described in A080577.

Examples

			a(2) = 5, because 33 has position 5 within the list of partitions of 6 in canonical ordering: 6, 51, 42, 411, 33, 321, 3111, 222, ... .
		

Crossrefs

Programs

  • Maple
    b:= proc(n) option remember;
         `if`(n=0, 1, b(n-1)+g(3*n, 2))
        end:
    g:= proc(n, i) option remember; `if`(n=0 or i=1, 1,
         `if`(i<1, 0, g(n-i, min(n-i, i))+g(n, i-1)))
        end:
    a:= n-> g(3*n$2)-b(n)+1:
    seq(a(n), n=0..35);
  • Mathematica
    b[n_] := b[n] = If[n == 0, 1, b[n - 1] + g[3n, 2]];
    g[n_, i_] := g[n, i] = If[n == 0 || i == 1, 1, If[i < 1, 0, g[n - i, Min[n - i, i]] + g[n, i - 1]]];
    a[n_] := g[3n, 3n] - b[n] + 1;
    a /@ Range[0, 35] (* Jean-François Alcover, Jan 06 2021, after Alois P. Heinz *)

Formula

a(n) ~ exp(Pi*sqrt(2*n)) / (4*3^(3/2)*n). - Vaclav Kotesovec, Feb 28 2020

A330693 Regular subtriangle of A328773: T(n,k) is the number of the balanced colored digraphs on n nodes with k colors, 1 <= k <= n.

Original entry on oeis.org

1, 3, 4, 16, 36, 64, 218, 1104, 2112, 4096, 9608, 90416, 266496, 528384, 1048576, 1540944, 30194176, 135032832, 269500416, 537919488, 1073741824
Offset: 1

Views

Author

Peter Dolland, Dec 25 2019

Keywords

Comments

The color count, k, is a measure of the differentiation of the nodes: k = 1 means no differentiation at all, so we have A000273. k = n means all nodes are taken to be different, and we have A053763. With increasing differentiation T(n,k) < T(n,k+1) for 1 <= k < n.

Examples

			The balanced color scheme [2,2,2] has with A330661 the index 5 in A328773. So there are T(6,3) = A328773(6,5) = 135032832 digraphs with 6 nodes two each in the same color.
Triangle T(n,k) begins:
        1;
        3,        4;
       16,       36,        64;
      218,     1104,      2112,      4096;
     9608,    90416,    266496,    528384,   1048576;
  1540944, 30194176, 135032832, 269500416, 537919488, 1073741824;
  ...
		

Crossrefs

Programs

  • PARI
    \\ here C(p) computes sequence value for given partition.
    permcount(v) = {my(m=1, s=0, k=0, t); for(i=1, #v, t=v[i]; k=if(i>1&&t==v[i-1], k+1, 1); m*=t*k; s+=t); s!/m}
    edges(v) = {sum(i=2, #v, sum(j=1, i-1, 2*gcd(v[i], v[j]))) + sum(i=1, #v, v[i]-1)}
    C(p)={((i, v)->if(i>#p, 2^edges(v), my(s=0); forpart(q=p[i], s+=permcount(q)*self()(i+1, concat(v, Vec(q)))); s/p[i]!))(1, [])}
    Row(n)={apply(C, vecsort([Vecrev(p) | p<-partitions(n),p[#p]-p[1]<=1], , 4))}
    { for(n=1, 6, print(Row(n))) }

Formula

T(n,1) = A000273(n).
T(n,n) = A053763(n) = 2^(n^2 - n).
T(n,k) = A328773(n,A330661(n,k)).
Showing 1-7 of 7 results.