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 10 results.

A001189 Number of degree-n permutations of order exactly 2.

Original entry on oeis.org

0, 1, 3, 9, 25, 75, 231, 763, 2619, 9495, 35695, 140151, 568503, 2390479, 10349535, 46206735, 211799311, 997313823, 4809701439, 23758664095, 119952692895, 618884638911, 3257843882623, 17492190577599, 95680443760575, 532985208200575, 3020676745975551
Offset: 1

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Author

Keywords

Comments

Number of set partitions of [n] into blocks of size 2 and 1 with at least one block of size 2. - Olivier Gérard, Oct 29 2007
For n>=2, number of standard Young tableaux with height <= n - 1. That is, all tableaux (A000085) but the one with just one column. - Joerg Arndt, Oct 24 2012

References

  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Column k=1 of A143911, column k=2 of A080510, A182222. - Alois P. Heinz, Oct 24 2012
Column k=2 of A057731. - Alois P. Heinz, Feb 14 2013

Programs

  • Magma
    m:=30; R:=PowerSeriesRing(Rationals(), m); b:=Coefficients(R!( Exp(x + x^2/2) -Exp(x) )); [0] cat [Factorial(n+1)*b[n]: n in [1..m-2]]; // G. C. Greubel, May 14 2019
    
  • Maple
    a:= proc(n) option remember; `if`(n<3, [0$2, 1][n+1],
          a(n-1) +(n-1) *(1+a(n-2)))
        end:
    seq(a(n), n=1..30);  # Alois P. Heinz, Oct 24 2012
    # alternative:
    A001189 := proc(n)
        local a,prs,p,k ;
        a := 0 ;
        for prs from 1 to n/2 do
            p := product(binomial(n-2*k,2),k=0..prs-1) ;
            a := a+p/prs!;
        end do:
        a;
    end proc:
    seq(A001189(n),n=1..13) ; # R. J. Mathar, Jan 04 2017
  • Mathematica
    RecurrenceTable[{a[1]==0,a[2]==1,a[n]==a[n-1]+(1+a[n-2])(n-1)},a[n],{n,25}] (* Harvey P. Dale, Jul 27 2011 *)
  • PARI
    {a(n) = sum(j=1,floor(n/2), n!/(j!*(n-2*j)!*2^j))}; \\ G. C. Greubel, May 14 2019
    
  • Sage
    m = 30; T = taylor(exp(x +x^2/2) - exp(x), x, 0, m); a=[factorial(n)*T.coefficient(x, n) for n in (0..m)]; a[1:] # G. C. Greubel, May 14 2019

Formula

E.g.f.: exp(x + x^2/2) - exp(x).
a(n) = A000085(n) - 1.
a(n) = b(n, 2), where b(n, d)=Sum_{k=1..n} (n-1)!/(n-k)! * Sum_{l:lcm{k, l}=d} b(n-k, l), b(0, 1)=1 is the number of degree-n permutations of order exactly d.
From Henry Bottomley, May 03 2001: (Start)
a(n) = a(n-1) + (1 + a(n-2))*(n-1).
a(n) = Sum_{j=1..floor(n/2)} n!/(j!*(n-2*j)!*(2^j)). (End)

A218262 Number of standard Young tableaux of n cells and height >= 10.

Original entry on oeis.org

1, 11, 121, 1001, 8086, 59228, 426673, 2946593, 20161558, 135303408, 904408398, 5995379358, 39727129830, 262629161094, 1739604051411, 11535387587595, 76763703224070, 512448824337780, 3436760740882050, 23151339236295810, 156789753069685500, 1067435349046248600
Offset: 10

Views

Author

Alois P. Heinz, Oct 24 2012

Keywords

Comments

Also number of self-inverse permutations in S_n with longest increasing subsequence of length >= 10.

Crossrefs

Column k=10 of A182222.

Formula

a(n) = A000085(n) - A212915(n) = A182172(n,n) - A182172(n,9).

A218263 Number of standard Young tableaux of n cells and height >= 3.

Original entry on oeis.org

1, 4, 16, 56, 197, 694, 2494, 9244, 35234, 139228, 566788, 2387048, 10343101, 46193866, 211775002, 997265204, 4809609062, 23758479340, 119952340180, 618883933480, 3257842530546, 17492187873444, 95680438560276, 532985197799976, 3020676725917252
Offset: 3

Views

Author

Alois P. Heinz, Oct 24 2012

Keywords

Comments

Also number of self-inverse permutations in S_n with longest increasing subsequence of length >= 3. a(3)=1: 123; a(4)=4: 1234, 1243, 1324, 2134.

Crossrefs

Column k=3 of A182222.

Programs

  • Maple
    b:= proc(n) b(n):= `if`(n<2, 1, b(n-1) +(n-1)*b(n-2)) end:
    a:= n-> b(n) -binomial(n, iquo(n, 2)):
    seq(a(n), n=3..30);
  • Mathematica
    b[n_] := b[n] = If[n<2, 1, b[n-1] + (n-1)*b[n-2]];
    a[n_] := b[n] - Binomial[n, Quotient[n, 2]];
    Table[a[n], {n, 3, 30}] (* Jean-François Alcover, Aug 23 2021, after Alois P. Heinz *)

Formula

a(n) = A000085(n) - A001405(n) = A182172(n,n) - A182172(n,2).
Conjecture: (n-6)*(n-3)*(n+1)*a(n) +(-n^3+6*n^2+11*n-36)*a(n-1) -(n-1)*(n^3-4*n^2-21*n+76)*a(n-2) +2*(n-1)*(n-2)*(3*n-19)*a(n-3) +4*(n-5)*(n-1)*(n-2)*(n-3)*a(n-4)=0. - R. J. Mathar, Jan 04 2017

A218264 Number of standard Young tableaux of n cells and height >= 4.

Original entry on oeis.org

1, 5, 25, 105, 441, 1785, 7308, 29898, 124641, 526669, 2276846, 10038964, 45353269, 209442533, 990777442, 4791502156, 23707812077, 119810145337, 618483875689, 3256714122209, 17488997849803, 95671400358075, 532959538382100, 3020603738202750, 17411069344112895
Offset: 4

Views

Author

Alois P. Heinz, Oct 24 2012

Keywords

Comments

Also number of self-inverse permutations in S_n with longest increasing subsequence of length >= 4. a(4)=1: 1234; a(5)=5: 12345, 12354, 12435, 13245, 21345.

Crossrefs

Column k=4 of A182222.

Programs

  • Maple
    a:= proc(n) option remember;
          `if`(n<5, [0$4, 1][n+1], ((-5-7*n+3*n^2)*a(n-1)
            +(n-1)*(n^2-n-11)*a(n-2) -2*n*(n-1)*(n-2)*a(n-3)
            -3*(n-1)*(n-2)*(n-3)*a(n-4))/((n+2)*(n-4)))
        end:
    seq(a(n), n=4..30);
  • Mathematica
    a[n_] := a[n] = If[n<5, {0,0,0,0,1}[[n+1]], ((-5-7n+3n^2)a[n-1] + (n-1)(n^2-n-11)a[n-2] - 2n(n-1)(n-2)a[n-3] - 3(n-1)(n-2)(n-3)a[n-4])/ ((n+2)(n-4))];
    Table[a[n], {n, 4, 30}] (* Jean-François Alcover, Aug 23 2021, after Alois P. Heinz *)

Formula

a(n) = A000085(n) - A001006(n) = A182172(n,n) - A182172(n,3).

A218265 Number of standard Young tableaux of n cells and height >= 5.

Original entry on oeis.org

1, 6, 36, 176, 856, 3952, 18272, 83524, 384463, 1777010, 8304636, 39254076, 188160268, 915651672, 4527595824, 22771294440, 116496899100, 606656445480, 3214574890480, 17337658462800, 95128543350576, 530998366724576, 3013524116661952, 17385349086129304
Offset: 5

Views

Author

Alois P. Heinz, Oct 24 2012

Keywords

Comments

Also number of self-inverse permutations in S_n with longest increasing subsequence of length >= 5. a(5)=1: 12345; a(6)=6: 123456, 123465, 123546, 124356, 132456, 213456.

Crossrefs

Column k=5 of A182222.

Programs

  • Maple
    a:= proc(n) option remember; `if`(n<13,
          [0$5, 1, 6, 36, 176, 856, 3952, 18272, 83524][n+1],
          ((n^4-2*n^3-179*n^2+256*n+804) *a(n-1)
          +(n-1)*(n^4+6*n^3-295*n^2+1108*n+100) *a(n-2)
          -4*(n-1)*(n-2)*(6*n^2-83*n+67) *a(n-3)
          -16*(n-11)*(n-1)*(n-3)*(n-2)^2 *a(n-4))/
          ((n-12)*(n-5)*(n+4)*(n+3)))
        end:
    seq(a(n), n=5..30);

Formula

a(n) = A000085(n) - A005817(n) = A182172(n,n) - A182172(n,4).

A218266 Number of standard Young tableaux of n cells and height >= 6.

Original entry on oeis.org

1, 7, 49, 273, 1506, 7788, 40161, 202917, 1028170, 5190328, 26375635, 134565795, 692890250, 3596739368, 18877483060, 100131220940, 537718999715, 2922918175965, 16100254700137, 89857257410905, 508473405642250, 2916903963927300, 16969580464205400
Offset: 6

Views

Author

Alois P. Heinz, Oct 24 2012

Keywords

Comments

Also number of self-inverse permutations in S_n with longest increasing subsequence of length >= 6. a(6)=1: 123456; a(7)=7: 1234567, 1234576, 1234657, 1235467, 1243567, 1324567, 2134567.

Crossrefs

Column k=6 of A182222.

Programs

  • Maple
    b:= proc(n) b(n):= `if`(n<2, 1, b(n-1) +(n-1)*b(n-2)) end:
    g:= proc(n) option remember; `if`(n<3, [1, 1, 2][n+1],
          ((3*n^2+17*n+15)*g(n-1) +(n-1)*(13*n+9)*g(n-2)
           -15*(n-1)*(n-2)*g(n-3)) / ((n+4)*(n+6)))
        end:
    a:= n-> b(n) -g(n):
    seq(a(n), n=6..30);

Formula

a(n) = A000085(n) - A049401(n) = A182172(n,n) - A182172(n,5).

A218267 Number of standard Young tableaux of n cells and height >= 7.

Original entry on oeis.org

1, 8, 64, 400, 2465, 14092, 80016, 442248, 2442351, 13375366, 73477622, 403703404, 2230591660, 12380801756, 69225756076, 389806286920, 2213844625658, 12681996193252, 73339826141716, 428242854338216, 2526129602115517, 15056977593085444, 90712249806247400
Offset: 7

Views

Author

Alois P. Heinz, Oct 24 2012

Keywords

Comments

Also number of self-inverse permutations in S_n with longest increasing subsequence of length >= 7. a(7)=1: 1234567; a(8)=8: 12345678, 12345687, 12345768, 12346578, 12354678, 12435678, 13245678, 21345678.

Crossrefs

Column k=7 of A182222.

Programs

  • Maple
    b:= proc(n) b(n):= `if`(n<2, 1, b(n-1) +(n-1)*b(n-2)) end:
    g:= proc(n) option remember;
          `if`(n<4, [1, 1, 2, 4][n+1], ((20*n^2+184*n+336)*g(n-1)
           +4*(n-1)*(10*n^2+58*n+33)*g(n-2) -144*(n-1)*(n-2)*g(n-3)
           -144*(n-1)*(n-2)*(n-3)*g(n-4)) / ((n+5)*(n+8)*(n+9)))
        end:
    a:= n-> b(n) -g(n):
    seq(a(n), n=7..30);

Formula

a(n) = A000085(n) - A007579(n) = A182172(n,n) - A182172(n,6).

A218268 Number of standard Young tableaux of n cells and height >= 8.

Original entry on oeis.org

1, 9, 81, 561, 3817, 23881, 147862, 886028, 5288933, 31178901, 183908244, 1081452450, 6381113064, 37719710024, 224141652938, 1337958249446, 8038507929319, 48593807722975, 295913856459150, 1814986751559300, 11220842616565050, 69921225307663290
Offset: 8

Views

Author

Alois P. Heinz, Oct 24 2012

Keywords

Comments

Also number of self-inverse permutations in S_n with longest increasing subsequence of length >= 8. a(8)=1: 12345678; a(9)=9: 123456789, 123456798, 123456879, 123457689, 123465789, 123546789, 124356789, 132456789, 213456789.

Crossrefs

Column k=8 of A182222.

Programs

  • Maple
    b:= proc(n) b(n):= `if`(n<2, 1, b(n-1) +(n-1)*b(n-2)) end:
    g:= proc(n) option remember; `if`(n<4, [1, 1, 2, 4][n+1],
          ((4*n^3+78*n^2+424*n+495)*g(n-1) +(n-1)*(34*n^2+280*n
          +305)*g(n-2) -2*(n-1)*(n-2)*(38*n+145)*g(n-3) -105*(n-1)
          *(n-2)*(n-3)*g(n-4)) / ((n+6)*(n+10)*(n+12)))
        end:
    a:= n-> b(n) -g(n):
    seq(a(n), n=8..30);

Formula

a(n) = A000085(n) - A007578(n) = A182172(n,n) - A182172(n,7).

A218269 Number of standard Young tableaux of n cells and height >= 9.

Original entry on oeis.org

1, 10, 100, 760, 5656, 38416, 257376, 1660416, 10640692, 67100072, 422374352, 2643349180, 16566306380, 103786892840, 652502735152, 4113403313016, 26057914447911, 165824119892086, 1061381766546172, 6832087071296824, 44260892997918920, 288574772339715376
Offset: 9

Views

Author

Alois P. Heinz, Oct 24 2012

Keywords

Comments

Also number of self-inverse permutations in S_n with longest increasing subsequence of length >= 9.

Crossrefs

Column k=9 of A182222.

Programs

  • Maple
    b:= proc(n) b(n):= `if`(n<2, 1, b(n-1) +(n-1)*b(n-2)) end:
    g:= proc(n) option remember; `if`(n<4, [1, 1, 2, 4][n+1],
          ((40*n^3+1084*n^2+8684*n+18480)*g(n-1) +16*(n-1)
          *(5*n^3+107*n^2+610*n+600)*g(n-2) -1024*(n-1)*(n-2)
          *(n+6)*g(n-3) -1024*(n-1)*(n-2)*(n-3)*(n+4)*g(n-4))/
           ((n+7)*(n+12)*(n+15)*(n+16)))
        end:
    a:= n-> b(n) -g(n):
    seq(a(n), n=9..30);

Formula

a(n) = A000085(n) - A007580(n) = A182172(n,n) - A182172(n,8).

A318289 Number of standard Young tableaux of 2n cells and height >= n.

Original entry on oeis.org

1, 2, 9, 56, 441, 3952, 40161, 442248, 5288933, 67100072, 904408398, 12777826272, 189324035423, 2917525618256, 46754429476800, 774965979970096, 13279872426589125, 234395323126241080, 4258775222885983350, 79442662095373693728, 1520453631213137081776
Offset: 0

Views

Author

Alois P. Heinz, Nov 04 2018

Keywords

Comments

Also number of self-inverse permutations of [2n] with longest increasing subsequence of length >= n.

Crossrefs

Cf. A182222.

Programs

  • Mathematica
    h[l_] := Module[{n = Length[l]}, Total[l]!/Product[Product[1+l[[i]]-j+Sum[ If[l[[k]] >= j, 1, 0], {k, i+1, n}], {j, 1, l[[i]]}], {i, 1, n}]];
    g[n_, i_, l_] := g[n, i, l] = If[n == 0, h[l], If[i < 1, 0, If[i == 1, h[Join[l, Array[1&, n]]], g[n, i-1, l] + If[i > n, 0, g[n-i, i, Append[l, i]]]]]];
    t[n_, k_] := g[n, n, {}] - If[k == 0, 0, g[n, k-1, {}]];
    a[n_] := a[n] = t[2n, n];
    Table[Print[n, " ", a[n]]; a[n], {n, 0, 20}] (* Jean-François Alcover, Sep 08 2021, after Alois P. Heinz in A182222 *)

Formula

a(n) = A182222(2n,n).
Showing 1-10 of 10 results.