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 1-10 of 14 results. Next

A303697 Number T(n,k) of permutations p of [n] whose difference between sum of up-jumps and sum of down-jumps equals k; triangle T(n,k), n>=0, min(0,1-n)<=k<=max(0,n-1), read by rows.

Original entry on oeis.org

1, 1, 1, 0, 1, 1, 1, 2, 1, 1, 1, 4, 5, 4, 5, 4, 1, 1, 11, 19, 19, 20, 19, 19, 11, 1, 1, 26, 82, 100, 101, 100, 101, 100, 82, 26, 1, 1, 57, 334, 580, 619, 619, 620, 619, 619, 580, 334, 57, 1, 1, 120, 1255, 3394, 4339, 4420, 4421, 4420, 4421, 4420, 4339, 3394, 1255, 120, 1
Offset: 0

Views

Author

Alois P. Heinz, Apr 28 2018

Keywords

Comments

An up-jump j occurs at position i in p if p_{i} > p_{i-1} and j is the index of p_i in the increasingly sorted list of those elements in {p_{i}, ..., p_{n}} that are larger than p_{i-1}. A down-jump j occurs at position i in p if p_{i} < p_{i-1} and j is the index of p_i in the decreasingly sorted list of those elements in {p_{i}, ..., p_{n}} that are smaller than p_{i-1}. First index in the lists is 1 here.

Examples

			Triangle T(n,k) begins:
:                               1                             ;
:                               1                             ;
:                          1,   0,   1                        ;
:                     1,   1,   2,   1,   1                   ;
:                1,   4,   5,   4,   5,   4,   1              ;
:           1,  11,  19,  19,  20,  19,  19,  11,   1         ;
:      1,  26,  82, 100, 101, 100, 101, 100,  82,  26,  1     ;
:  1, 57, 334, 580, 619, 619, 620, 619, 619, 580, 334, 57, 1  ;
		

Crossrefs

Programs

  • Maple
    b:= proc(u, o) option remember; expand(`if`(u+o=0, 1,
          add(b(u-j, o+j-1)*x^(-j), j=1..u)+
          add(b(u+j-1, o-j)*x^( j), j=1..o)))
        end:
    T:= n-> (p-> seq(coeff(p, x, i), i=ldegree(p)..degree(p)))(
            `if`(n=0, 1, add(b(j-1, n-j), j=1..n))):
    seq(T(n), n=0..12);
  • Mathematica
    b[u_, o_] := b[u, o] = Expand[If[u+o == 0, 1,
         Sum[b[u-j, o+j-1] x^-j, {j, 1, u}] +
         Sum[b[u+j-1, o-j] x^j, {j, 1, o}]]];
    T[0] = {1};
    T[n_] := x^n Sum[b[j-1, n-j], {j, 1, n}] // CoefficientList[#, x]& // Rest;
    T /@ Range[0, 12] // Flatten (* Jean-François Alcover, Feb 20 2021, after Alois P. Heinz *)

Formula

T(n,0) = A153229(n) for n > 0.
T(n,1) = A005165(n-1) for n > 0.
T(n+1,n-1) = A000295(n).
T(n,k) = T(n,-k).
Sum_{k=0..n-1} k^2 * T(n,k) = A001720(n+2) for n>1.

A291685 Number of permutations p of [n] such that 0p has a nonincreasing jump sequence.

Original entry on oeis.org

1, 1, 2, 5, 16, 52, 189, 683, 2621, 10061, 40031, 159201, 650880, 2657089, 11062682, 46065143, 194595138, 822215099, 3513875245, 15021070567, 64785349064, 279575206629, 1214958544538, 5283266426743, 23106210465665, 101120747493793, 444614706427665
Offset: 0

Views

Author

Alois P. Heinz, Aug 29 2017

Keywords

Comments

An up-jump j occurs at position i in p if p_{i} > p_{i-1} and j is the index of p_i in the increasingly sorted list of those elements in {p_{i}, ..., p_{n}} that are larger than p_{i-1}. A down-jump j occurs at position i in p if p_{i} < p_{i-1} and j is the index of p_i in the decreasingly sorted list of those elements in {p_{i}, ..., p_{n}} that are smaller than p_{i-1}. First index in the lists is 1 here.

Examples

			a(3) = 5 = 6 - 1 counts all permutations of {1,2,3} except 132 with jump sequence 1, 2, 1.
		

Crossrefs

Row sums and main diagonal (shifted) of A291684.

Programs

  • Maple
    b:= proc(u, o, t) option remember; `if`(u+o=0, 1,
          add(b(u-j, o+j-1, j), j=1..min(t, u))+
          add(b(u+j-1, o-j, j), j=1..min(t, o)))
        end:
    a:= n-> b(0, n$2):
    seq(a(n), n=0..30);
  • Mathematica
    b[u_, o_, t_] := b[u, o, t] = If[u+o == 0, 1,
         Sum[b[u-j, o+j-1, j], {j, Min[t, u]}]+
         Sum[b[u+j-1, o-j, j], {j, Min[t, o]}]];
    a[n_] := b[0, n, n];
    Table[a[n], {n, 0, 30}] (* Jean-François Alcover, Aug 30 2021, after Alois P. Heinz *)

A303204 Number of permutations p of [n] such that 0p has a nonincreasing jump sequence beginning with ceiling(n/2).

Original entry on oeis.org

1, 1, 1, 2, 5, 12, 36, 98, 327, 988, 3392, 10872, 38795, 129520, 469662, 1609176, 5935728, 20786804, 77416352, 274792342, 1035050705, 3719296036, 14094000938, 51119572738, 195075365778, 712918642042, 2734475097609, 10055531355652, 38747262233793
Offset: 0

Views

Author

Alois P. Heinz, Apr 19 2018

Keywords

Comments

An up-jump j occurs at position i in p if p_{i} > p_{i-1} and j is the index of p_i in the increasingly sorted list of those elements in {p_{i}, ..., p_{n}} that are larger than p_{i-1}. A down-jump j occurs at position i in p if p_{i} < p_{i-1} and j is the index of p_i in the decreasingly sorted list of those elements in {p_{i}, ..., p_{n}} that are smaller than p_{i-1}. First index in the lists is 1 here.

Crossrefs

Bisections give A291688 (even part), A303203 (odd part).
Cf. A291684.

Programs

  • Maple
    b:= proc(u, o, t) option remember; `if`(u+o=0, 1,
          add(b(sort([u-j, o+j-1])[], j), j=1..min(t, u))+
          add(b(sort([u+j-1, o-j])[], j), j=1..min(t, o)))
        end:
    a:= n-> `if`(n=0, 1, (j-> b(0, n, j)-b(0, n, j-1))(ceil(n/2))):
    seq(a(n), n=0..30);
  • Mathematica
    b[u_, o_, t_] := b[u, o, t] = If[u+o == 0, 1,
         Sum[b[Sequence @@ Sort[{u-j, o+j-1}], j], {j, Min[t, u]}]+
         Sum[b[Sequence @@ Sort[{u+j-1, o-j}], j], {j, Min[t, o]}]];
    a[n_] := If[n == 0, 1,
         Function[j, b[0, n, j] - b[0, n, j-1]][Ceiling[n/2]]];
    Table[a[n], {n, 0, 30}]; (* Jean-François Alcover, Aug 30 2021, after Alois P. Heinz *)

Formula

a(n) = A291684(n,ceiling(n/2)).

A291688 Number of permutations p of [2n] such that 0p has a nonincreasing jump sequence beginning with n.

Original entry on oeis.org

1, 1, 5, 36, 327, 3392, 38795, 469662, 5935728, 77416352, 1035050705, 14094000938, 195075365778, 2734475097609, 38747262233793, 554199475506095, 7990492729051526, 115995691148658656, 1694340616136589743, 24882428969673439384, 367160435328847044586
Offset: 0

Views

Author

Alois P. Heinz, Aug 29 2017

Keywords

Comments

An up-jump j occurs at position i in p if p_{i} > p_{i-1} and j is the index of p_i in the increasingly sorted list of those elements in {p_{i}, ..., p_{n}} that are larger than p_{i-1}. A down-jump j occurs at position i in p if p_{i} < p_{i-1} and j is the index of p_i in the decreasingly sorted list of those elements in {p_{i}, ..., p_{n}} that are smaller than p_{i-1}. First index in the lists is 1 here.

Examples

			a(2) = 5: 2134, 2314, 2341, 2413, 2431.
		

Crossrefs

Cf. A291684.
Bisection (even part) of A303204.

Programs

  • Maple
    b:= proc(u, o, t) option remember; `if`(u+o=0, 1,
          add(b(u-j, o+j-1, j), j=1..min(t, u))+
          add(b(u+j-1, o-j, j), j=1..min(t, o)))
        end:
    a:= n-> b(0, 2*n, n)-`if`(n=0, 0, b(0, 2*n, n-1)):
    seq(a(n), n=0..25);
  • Mathematica
    b[u_, o_, t_] := b[u, o, t] = If[u + o == 0, 1,
         Sum[b[u - j, o + j - 1, j], {j, Min[t, u]}] +
         Sum[b[u + j - 1, o - j, j], {j, Min[t, o]}]];
    a[n_] :=  b[0, 2n, n] - If[n == 0, 0, b[0, 2n, n - 1]];
    Table[a[n], {n, 0, 25}] (* Jean-François Alcover, Aug 30 2021, after Alois P. Heinz *)

Formula

a(n) = A291684(2n,n).

A303203 Number of permutations p of [2n+1] such that 0p has a nonincreasing jump sequence beginning with n+1.

Original entry on oeis.org

1, 2, 12, 98, 988, 10872, 129520, 1609176, 20786804, 274792342, 3719296036, 51119572738, 712918642042, 10055531355652, 143287150725298, 2058368140071146, 29796314629826814, 434051906728752164, 6359063811707227298, 93635249115751389952, 1385028309353547034876
Offset: 0

Views

Author

Alois P. Heinz, Apr 19 2018

Keywords

Comments

An up-jump j occurs at position i in p if p_{i} > p_{i-1} and j is the index of p_i in the increasingly sorted list of those elements in {p_{i}, ..., p_{n}} that are larger than p_{i-1}. A down-jump j occurs at position i in p if p_{i} < p_{i-1} and j is the index of p_i in the decreasingly sorted list of those elements in {p_{i}, ..., p_{n}} that are smaller than p_{i-1}. First index in the lists is 1 here.

Crossrefs

Bisection (odd part) of A303204.
Cf. A291684.

Programs

  • Maple
    b:= proc(u, o, t) option remember; `if`(u+o=0, 1,
          add(b(sort([u-j, o+j-1])[], j), j=1..min(t, u))+
          add(b(sort([u+j-1, o-j])[], j), j=1..min(t, o)))
        end:
    a:= n-> b(0, 2*n+1, n+1)-b(0, 2*n+1, n):
    seq(a(n), n=0..25);
  • Mathematica
    b[u_, o_, t_] := b[u, o, t] = If[u+o == 0, 1,
         Sum[b[u-j, o+j-1, j], {j, 1, Min[t, u]}] +
         Sum[b[u+j-1, o-j, j], {j, 1, Min[t, o]}]];
    a[n_] := b[0, 2n+1, n+1] - b[0, 2n+1, n];
    a /@ Range[0, 25] (* Jean-François Alcover, Sep 01 2021, after Alois P. Heinz *)

Formula

a(n) = A291684(2n+1,n+1).

A292168 Number of permutations p of [n] such that 0p has a nonincreasing jump sequence beginning with two.

Original entry on oeis.org

1, 2, 5, 9, 17, 31, 57, 101, 185, 333, 599, 1089, 1975, 3563, 6505, 11829, 21455, 39257, 71641, 130403, 239193, 437677, 799127, 1468777, 2693853, 4930871, 9079127, 16684737, 30605159, 56441227, 103900161, 190934999, 352606721, 650072239, 1196527319, 2212404279
Offset: 2

Views

Author

Alois P. Heinz, Sep 10 2017

Keywords

Comments

An up-jump j occurs at position i in p if p_{i} > p_{i-1} and j is the index of p_i in the increasingly sorted list of those elements in {p_{i}, ..., p_{n}} that are larger than p_{i-1}. A down-jump j occurs at position i in p if p_{i} < p_{i-1} and j is the index of p_i in the decreasingly sorted list of those elements in {p_{i}, ..., p_{n}} that are smaller than p_{i-1}. First index in the lists is 1 here.

Examples

			a(2) = 1: 21.
a(3) = 2: 213, 231.
a(4) = 5: 2134, 2314, 2341, 2413, 2431.
a(5) = 9: 21345, 23145, 23415, 23451, 24135, 24153, 24315, 24351, 24531.
a(6) = 17: 213456, 231456, 234156, 234516, 234561, 241356, 241536, 241563, 243156, 243516, 243561, 245316, 245361, 245631, 246315, 246351, 246531.
		

Crossrefs

Column k=2 of A291684.

Programs

  • Maple
    b:= proc(u, o, t) option remember; `if`(u+o=0, 1,
          add(b(u-j, o+j-1, j), j=1..min(t, u))+
          add(b(u+j-1, o-j, j), j=1..min(t, o)))
        end:
    a:= n-> b(0, n, 2)-b(0, n, 1):
    seq(a(n), n=2..50);

A292169 Number of permutations p of [n] such that 0p has a nonincreasing jump sequence beginning with three.

Original entry on oeis.org

2, 5, 12, 36, 81, 174, 413, 889, 1870, 4031, 8490, 17580, 36647, 75801, 154676, 316873, 646614, 1309277, 2653548, 5358828, 10786403, 21697201, 43539382, 87208388, 174392929, 348359875, 694913277, 1384281163, 2755398784, 5476741024, 10878139055, 21590446589
Offset: 3

Views

Author

Alois P. Heinz, Sep 10 2017

Keywords

Comments

An up-jump j occurs at position i in p if p_{i} > p_{i-1} and j is the index of p_i in the increasingly sorted list of those elements in {p_{i}, ..., p_{n}} that are larger than p_{i-1}. A down-jump j occurs at position i in p if p_{i} < p_{i-1} and j is the index of p_i in the decreasingly sorted list of those elements in {p_{i}, ..., p_{n}} that are smaller than p_{i-1}. First index in the lists is 1 here.

Examples

			a(3) = 2: 312, 321.
a(4) = 5: 3124, 3142, 3214, 3241, 3421
a(5) = 12: 31245, 31425, 31452, 32145, 32415, 32451, 34215, 34251, 34521, 35214, 35241, 35421.
		

Crossrefs

Column k=3 of A291684.

Programs

  • Maple
    b:= proc(u, o, t) option remember; `if`(u+o=0, 1,
          add(b(u-j, o+j-1, j), j=1..min(t, u))+
          add(b(u+j-1, o-j, j), j=1..min(t, o)))
        end:
    a:= n-> b(0, n, 3)-b(0, n, 2):
    seq(a(n), n=3..50);

A292170 Number of permutations p of [n] such that 0p has a nonincreasing jump sequence beginning with four.

Original entry on oeis.org

5, 14, 36, 98, 327, 788, 1890, 4523, 11483, 27209, 61983, 139568, 323531, 730494, 1618531, 3543509, 7851556, 17204960, 37331967, 80312122, 173234350, 372183777, 794587802, 1686743710, 3579347697, 7578433425, 15984149737, 33580700124, 70467297970, 147600492302
Offset: 4

Views

Author

Alois P. Heinz, Sep 10 2017

Keywords

Comments

An up-jump j occurs at position i in p if p_{i} > p_{i-1} and j is the index of p_i in the increasingly sorted list of those elements in {p_{i}, ..., p_{n}} that are larger than p_{i-1}. A down-jump j occurs at position i in p if p_{i} < p_{i-1} and j is the index of p_i in the decreasingly sorted list of those elements in {p_{i}, ..., p_{n}} that are smaller than p_{i-1}. First index in the lists is 1 here.

Examples

			a(4) = 5: 4123, 4132, 4213, 4231, 4321.
a(5) = 14: 41235, 41325, 41352, 41523, 41532, 42135, 42315, 42351, 42513, 42531, 43215, 43251, 43521, 45321.
a(6) = 36: 412356, 413256, 413526, 413562, 413625, 413652, 415236, 415263, 415326, 415362, 415632, 421356, 423156, 423516, 423561, 425136, 425163, 425316, 425361, 425631, 432156, 432516, 432561, 435216, 435261, 435621, 453216, 453261, 453621, 456321, 463125, 463152, 463215, 463251, 463521, 465321.
		

Crossrefs

Column k=4 of A291684.

Programs

  • Maple
    b:= proc(u, o, t) option remember; `if`(u+o=0, 1,
          add(b(u-j, o+j-1, j), j=1..min(t, u))+
          add(b(u+j-1, o-j, j), j=1..min(t, o)))
        end:
    a:= n-> b(0, n, 4)-b(0, n, 3):
    seq(a(n), n=4..50);

A292171 Number of permutations p of [n] such that 0p has a nonincreasing jump sequence beginning with five.

Original entry on oeis.org

16, 47, 117, 327, 988, 3392, 8739, 21372, 53596, 135791, 362528, 887060, 2117839, 4997836, 11731828, 28229247, 66196942, 152418888, 347010327, 784580873, 1794241712, 4064606075, 9109879761, 20253187230, 44774963928, 99368298849, 219638865759, 482519177252
Offset: 5

Views

Author

Alois P. Heinz, Sep 10 2017

Keywords

Comments

An up-jump j occurs at position i in p if p_{i} > p_{i-1} and j is the index of p_i in the increasingly sorted list of those elements in {p_{i}, ..., p_{n}} that are larger than p_{i-1}. A down-jump j occurs at position i in p if p_{i} < p_{i-1} and j is the index of p_i in the decreasingly sorted list of those elements in {p_{i}, ..., p_{n}} that are smaller than p_{i-1}. First index in the lists is 1 here.

Examples

			a(5) = 16: 51234, 51324, 51342, 51423, 51432, 52134, 52314, 52341, 52413, 52431, 53124, 53142, 53214, 53241, 53421, 54321.
a(6) = 47: 512346, 513246, 513426, 513462, 513624, ..., 543216, 543261, 543621, 546321, 564321.
		

Crossrefs

Column k=5 of A291684.

Programs

  • Maple
    b:= proc(u, o, t) option remember; `if`(u+o=0, 1,
          add(b(u-j, o+j-1, j), j=1..min(t, u))+
          add(b(u+j-1, o-j, j), j=1..min(t, o)))
        end:
    a:= n-> b(0, n, 5)-b(0, n, 4):
    seq(a(n), n=5..50);

A292172 Number of permutations p of [n] such that 0p has a nonincreasing jump sequence beginning with six.

Original entry on oeis.org

52, 166, 425, 1116, 3392, 10872, 38795, 102634, 260334, 651704, 1707641, 4477199, 12277412, 30970764, 75239813, 181934538, 440594545, 1063081418, 2625678546, 6286974074, 14803016600, 34534616815, 80129926919, 185059517397, 431845849360, 997735570874
Offset: 6

Views

Author

Alois P. Heinz, Sep 10 2017

Keywords

Comments

An up-jump j occurs at position i in p if p_{i} > p_{i-1} and j is the index of p_i in the increasingly sorted list of those elements in {p_{i}, ..., p_{n}} that are larger than p_{i-1}. A down-jump j occurs at position i in p if p_{i} < p_{i-1} and j is the index of p_i in the decreasingly sorted list of those elements in {p_{i}, ..., p_{n}} that are smaller than p_{i-1}. First index in the lists is 1 here.

Examples

			a(6) = 52: 612345, 613245, 613425, 613452, 613524, 613542, 614235, 614253, 614325, 614352, 614532, 615234, 615243, 615324, 615342, 615432, 621345, 623145, 623415, 623451, 624135, 624153, 624315, 624351, 624531, 625134, 625143, 625314, 625341, 625431, 631245, 631425, 631452, 632145, 632415, 632451, 634215, 634251, 634521, 635214, 635241, 635421, 642135, 642315, 642351, 642513, 642531, 643215, 643251, 643521, 645321, 654321.
		

Crossrefs

Column k=6 of A291684.

Programs

  • Maple
    b:= proc(u, o, t) option remember; `if`(u+o=0, 1,
          add(b(u-j, o+j-1, j), j=1..min(t, u))+
          add(b(u+j-1, o-j, j), j=1..min(t, o)))
        end:
    a:= n-> b(0, n, 6)-b(0, n, 5):
    seq(a(n), n=6..50);
Showing 1-10 of 14 results. Next