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.

Previous Showing 11-16 of 16 results.

A261799 Number of 7-compositions of n: matrices with 7 rows of nonnegative integers with positive column sums and total element sum n.

Original entry on oeis.org

1, 7, 77, 819, 8687, 92141, 977347, 10366833, 109962202, 1166381804, 12371946734, 131230670312, 1391978902090, 14764881252772, 156612803600094, 1661210126351328, 17620647995924820, 186904251828901124, 1982515022137687464, 21028766197355391048
Offset: 0

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Author

Alois P. Heinz, Sep 01 2015

Keywords

Comments

Also the number of compositions of n where each part i is marked with a word of length i over a septenary alphabet whose letters appear in alphabetical order.

Crossrefs

Column k=7 of A261780.

Programs

  • Maple
    a:= proc(n) option remember; `if`(n=0, 1,
          add(a(n-j)*binomial(j+6, 6), j=1..n))
        end:
    seq(a(n), n=0..20);

Formula

G.f.: (1-x)^7/(2*(1-x)^7-1).
a(n) = A261780(n,7).
a(n) = Sum_{k>=0} (1/2)^(k+1) * binomial(n-1+7*k,n). - Seiichi Manyama, Aug 06 2024

A261800 Number of 8-compositions of n: matrices with 8 rows of nonnegative integers with positive column sums and total element sum n.

Original entry on oeis.org

1, 8, 100, 1208, 14554, 175352, 2112772, 25456328, 306717703, 3695574048, 44527157584, 536497912672, 6464145163032, 77885061063584, 938419943222768, 11306815168562400, 136233325153964242, 1641445323534504928, 19777413104380161776, 238293693669343744032
Offset: 0

Views

Author

Alois P. Heinz, Sep 01 2015

Keywords

Comments

Also the number of compositions of n where each part i is marked with a word of length i over an octonary alphabet whose letters appear in alphabetical order.

Crossrefs

Column k=8 of A261780.

Programs

  • Maple
    a:= proc(n) option remember; `if`(n=0, 1,
          add(a(n-j)*binomial(j+7, 7), j=1..n))
        end:
    seq(a(n), n=0..20);
  • Mathematica
    CoefficientList[Series[(1-x)^8/(2(1-x)^8-1),{x,0,30}],x] (* or  *) LinearRecurrence[{16,-56,112,-140,112,-56,16,-2},{1,8,100,1208,14554,175352,2112772,25456328,306717703},30] (* Harvey P. Dale, Jul 15 2023 *)

Formula

G.f.: (1-x)^8/(2*(1-x)^8-1).
a(n) = A261780(n,8).
a(n) = Sum_{k>=0} (1/2)^(k+1) * binomial(n-1+8*k,n). - Seiichi Manyama, Aug 06 2024

A261801 Number of 9-compositions of n: matrices with 9 rows of nonnegative integers with positive column sums and total element sum n.

Original entry on oeis.org

1, 9, 126, 1704, 22986, 310086, 4183260, 56435004, 761346207, 10271072557, 138563678736, 1869317246556, 25218347263608, 340212470558832, 4589695110222504, 61918074814238448, 835316485437693186, 11268981358631127288, 152026139882340589466
Offset: 0

Views

Author

Alois P. Heinz, Sep 01 2015

Keywords

Comments

Also the number of compositions of n where each part i is marked with a word of length i over a nonary alphabet whose letters appear in alphabetical order.

Crossrefs

Column k=9 of A261780.

Programs

  • Maple
    a:= proc(n) option remember; `if`(n=0, 1,
          add(a(n-j)*binomial(j+8, 8), j=1..n))
        end:
    seq(a(n), n=0..20);

Formula

G.f.: (1-x)^9/(2*(1-x)^9-1).
a(n) = A261780(n,9).
a(n) = Sum_{k>=0} (1/2)^(k+1) * binomial(n-1+9*k,n). - Seiichi Manyama, Aug 06 2024

A261802 Number of 10-compositions of n: matrices with 10 rows of nonnegative integers with positive column sums and total element sum n.

Original entry on oeis.org

1, 10, 155, 2320, 34640, 517252, 7723970, 115339960, 1722340115, 25719233330, 384058268507, 5735036957760, 85639736481880, 1278834734405320, 19096488909285540, 285162639746429024, 4258255614078447290, 63587365059302801520, 949532710487622388080
Offset: 0

Views

Author

Alois P. Heinz, Sep 01 2015

Keywords

Comments

Also the number of compositions of n where each part i is marked with a word of length i over a denary alphabet whose letters appear in alphabetical order.

Crossrefs

Column k=10 of A261780.

Programs

  • Maple
    a:= proc(n) option remember; `if`(n=0, 1,
          add(a(n-j)*binomial(j+9, 9), j=1..n))
        end:
    seq(a(n), n=0..20);

Formula

G.f.: (1-x)^10/(2*(1-x)^10-1).
a(n) = A261780(n,10).
a(n) = Sum_{k>=0} (1/2)^(k+1) * binomial(n-1+10*k,n). - Seiichi Manyama, Aug 06 2024

A382924 Number of m-compositions of n with n zeros.

Original entry on oeis.org

1, 2, 13, 70, 336, 2076, 11091, 65210, 365661, 2159354, 11713047, 71427504, 392916687, 2245186352, 13527678851, 73679458270, 429472428457, 2553994191220, 14264421153074, 80483620074092, 489077890675807, 2768919905996888, 15394229582049408, 91794448088043258
Offset: 0

Views

Author

John Tyler Rascoe, Apr 09 2025

Keywords

Comments

For some m > 0, an m-composition of n is a rectangular array of nonnegative integers with m rows, at least one nonzero entry in each column, and having the sum of all entries equal to n.

Examples

			a(2) = 13 counts:
  [2]  [0]  [0]  [1]  [1]  [1]  [0]  [0]  [0]  [1][1]  [1][0]  [0][0]  [0][1]
  [0]  [2]  [0]  [1]  [0]  [0]  [1]  [1]  [0]  [0][0], [0][1], [1][1], [1][0].
  [0], [0], [2], [0]  [1]  [0]  [1]  [0]  [1]
                 [0], [0], [1], [0], [1], [1],
		

Crossrefs

Cf. A038207, A101509, A181331, A261780, A323429, A382820, (main diagonal of A382923).

Programs

  • PARI
    G_tx(max_row) = {my(row = max_row, N = row*2, m = List([concat([1],vector(row-1,i,0))]), x='x+O('x^N), h=1 + sum(m=1,N,-1+ 1/(1 + t^m - (t + x/(1-x))^m))); for(n=1,row, listput(m,Vecrev(polcoeff(h, n))[1..row])); matrix(row, row, i,j, m[i][j])}
    A382924(max_n) ={my(A=G_tx(max_n)); vector(max_n,i,A[i,i])}
    A382924(20)

Formula

a(n) = [(x*t)^n] 1 + Sum_{m>0} -1 + 1/(1 + t^m - (t + x/(1 - x))^m).

A383256 Number of n X n matrices of nonnegative entries with all columns summing to n and no horizontally adjacent zeros.

Original entry on oeis.org

1, 1, 7, 343, 125465, 366908001, 8698468668251, 1708834003295306868, 2810884261025802145414705, 39088555382409783097546399456477, 4626844513673581956954679383115038810744, 4688191496359773864437279635019555242588548880831
Offset: 0

Views

Author

John Tyler Rascoe, Apr 21 2025

Keywords

Examples

			a(1) = 1: [1]
a(2) = 7: [1,1]   [1,0]   [1,2]   [0,1]   [2,1]   [0,2]   [2,0]
          [1,1],  [1,2],  [1,0],  [2,1],  [0,1],  [2,0],  [0,2].
		

Crossrefs

Programs

  • Python
    # see links

Extensions

a(10)-a(11) from Bert Dobbelaere, Apr 23 2025
Previous Showing 11-16 of 16 results.