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 1-3 of 3 results.

A368565 a(n) = number of pairs (p,q) of partitions of n such that d(p,q) < o(p,q), where d and o are distance functions; see Comments.

Original entry on oeis.org

0, 0, 0, 0, 0, 30, 106, 316, 652, 1388, 2618, 5170, 9164, 16790, 29046, 50714, 84732, 143588, 234048, 385210, 617050, 990868, 1558310, 2459300, 3806838, 5900184
Offset: 1

Views

Author

Clark Kimberling, Dec 31 2023

Keywords

Comments

The definition of d depends on the greedy ordering of the partitions p(i) of n; that is, p(1) >= p(2) >= ... >= p(k), where k = A000041(n); see A366156. The ordinal distance o is defined by o(p(i),p(j)) = |i-j|.

Examples

			The 5 partitions of 4 are (p(1),p(2),p(3),p(4),p(5)) = (4,21,22,211,1111). The following table shows the 25 pairs d(p(i),q(j)) and o(p(i),q(j)):
          |    4   31   22   211  1111
------------------------------------------------
   4 d    |    0    2    4    4    6
     o    |    0    1    2    3    4
  31 d    |    2    0    2    2    4
     o    |    1    0    1    2    3
  22 d    |    4    2    0    2    4
     o    |    2    1    0    1    2
 211 d    |    4    2    2    0    2
     o    |    3    2    1    0    1
1111 d    |    6    4    4    2    0
     o    |    4    3    2    1    0
The table shows 0 pairs (p,q) for which d(p,q) < o(p,q), so a(4) = 0.
		

Crossrefs

Programs

  • Mathematica
    c[n_] := PartitionsP[n];
    q[n_, k_] := q[n, k] = IntegerPartitions[n][[k]];
    r[n_, k_] := r[n, k] = Join[q[n, k], ConstantArray[0, n - Length[q[n, k]]]];
    d[u_, v_] := Total[Abs[u - v]];
    p[n_] := Flatten[Table[d[r[n, j], r[n, k]] - Abs[j - k], {j, 1, c[n]}, {k, 1, c[n]}]];
    Table[Count[p[n], 0], {n, 1, 16}]  (* A368565  *)
    Table[Length[Select[p[n], Sign[#] == -1 &]], {n, 1,16}]  (* A368566 *)
    Table[Length[Select[p[n], Sign[#] == 1 &]], {n, 1, 16}]  (* A368567 *)

Formula

A368564(n) + a(n) + A368566(n) = A001255(n) for n >= 1.

A368566 a(n) = number of pairs (p,q) of partitions of n such that d(p,q) > o(p,q), where d and o are distance functions; see Comments.

Original entry on oeis.org

0, 2, 6, 18, 34, 48, 62, 108, 166, 242, 334, 512, 706, 984, 1368, 1876, 2492, 3360, 4422, 5848, 7574, 9792, 12596, 16130, 20412, 25850
Offset: 1

Views

Author

Clark Kimberling, Dec 31 2023

Keywords

Comments

The definition of d depends on the greedy ordering of the partitions p(i) of n; that is, p(1) >= p(2) >= ... >= p(k), where k = A000041(n); see A366156. The ordinal distance o is defined by o(p(i),p(j)) = |i-j|.

Examples

			The 5 partitions of 4 are (p(1),p(2),p(3),p(4),p(5)) = (4,21,22,211,1111). The following table shows the 25 pairs d(p(i),q(j)) and o(p(i),q(j)):
          |    4   31   22   211  1111
------------------------------------------------
   4 d    |    0    2    4    4    6
     o    |    0    1    2    3    4
  31 d    |    2    0    2    2    4
     o    |    1    0    1    2    3
  22 d    |    4    2    0    2    4
     o    |    2    1    0    1    2
 211 d    |    4    2    2    0    2
     o    |    3    2    1    0    1
1111 d    |    6    4    4    2    0
     o    |    4    3    2    1    0
The table shows 18 pairs (p,q) for which d(p,q) > o(p,q), so a(4) = 18.
		

Crossrefs

Programs

  • Mathematica
    c[n_] := PartitionsP[n];
    q[n_, k_] := q[n, k] = IntegerPartitions[n][[k]];
    r[n_, k_] := r[n, k] = Join[q[n, k], ConstantArray[0, n - Length[q[n, k]]]];
    d[u_, v_] := Total[Abs[u - v]];
    p[n_] := Flatten[Table[d[r[n, j], r[n, k]] - Abs[j - k], {j, 1, c[n]}, {k, 1, c[n]}]];
    Table[Count[p[n], 0], {n, 1, 16}]  (* A368565  *)
    Table[Length[Select[p[n], Sign[#] == -1 &]], {n, 1,16}]  (* A368566 *)
    Table[Length[Select[p[n], Sign[#] == 1 &]], {n, 1, 16}]  (* A368567 *)

Formula

A368564(n) + A368565(n) + a(n) = A001255(n) for n >= 1.

A368564 a(n) = number of pairs (p,q) of partitions of n such that d(p,q) = o(p,q), where d and o are distance functions; see Comments.

Original entry on oeis.org

1, 2, 3, 7, 15, 43, 57, 60, 82, 134, 184, 247, 331, 451, 562, 771, 985, 1277, 1630, 2071, 2640, 3344, 4119, 5195, 6514, 8062
Offset: 1

Views

Author

Clark Kimberling, Dec 31 2023

Keywords

Comments

The definition of d depends on the greedy ordering of the partitions p(i) of n; that is, p(1) >= p(2) >= ... >= p(k), where k = A000041(n); see A366156. The ordinal distance o is defined by o(p(i),p(j)) = |i-j|.

Examples

			The 5 partitions of 4 are (p(1),p(2),p(3),p(4),p(5)) = (4,21,22,211,1111). The following table shows the 25 pairs d(p(i),q(j)) and o(p(i),q(j)):
          |    4   31   22   211  1111
------------------------------------------------
   4 d    |    0    2    4    4    6
     o    |    0    1    2    3    4
  31 d    |    2    0    2    2    4
     o    |    1    0    1    2    3
  22 d    |    4    2    0    2    4
     o    |    2    1    0    1    2
 211 d    |    4    2    2    0    2
     o    |    3    2    1    0    1
1111 d    |    6    4    4    2    0
     o    |    4    3    2    1    0
The table shows 7 pairs (p,q) for which d(p,q) = o(p,q), so a(4) = 7.
		

Crossrefs

Programs

  • Mathematica
    c[n_] := PartitionsP[n];
    q[n_, k_] := q[n, k] = IntegerPartitions[n][[k]];
    r[n_, k_] := r[n, k] = Join[q[n, k], ConstantArray[0, n - Length[q[n, k]]]];
    d[u_, v_] := Total[Abs[u - v]];
    p[n_] := Flatten[Table[d[r[n, j], r[n, k]] - Abs[j - k], {j, 1, c[n]}, {k, 1, c[n]}]];
    Table[Count[p[n], 0], {n, 1, 16}]  (* A368565  *)
    Table[Length[Select[p[n], Sign[#] == -1 &]], {n, 1,16}]  (* A368566 *)
    Table[Length[Select[p[n], Sign[#] == 1 &]], {n, 1, 16}]  (* A368567 *)

Formula

a(n) + A368565(n) + A368566(n) = A001255(n) for n >= 1.
Showing 1-3 of 3 results.