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 41-48 of 48 results.

A349153 Numbers k such that the k-th composition in standard order has sum equal to twice its reverse-alternating sum.

Original entry on oeis.org

0, 11, 12, 14, 133, 138, 143, 148, 155, 158, 160, 168, 179, 182, 188, 195, 198, 204, 208, 216, 227, 230, 236, 240, 248, 2057, 2066, 2071, 2077, 2084, 2091, 2094, 2101, 2106, 2111, 2120, 2131, 2134, 2140, 2149, 2154, 2159, 2164, 2171, 2174, 2192, 2211, 2214
Offset: 1

Views

Author

Gus Wiseman, Nov 17 2021

Keywords

Comments

The k-th composition in standard order (graded reverse-lexicographic, A066099) is obtained by taking the set of positions of 1's in the reversed binary expansion of k, prepending 0, taking first differences, and reversing again. This gives a bijective correspondence between nonnegative integers and integer compositions.
The reverse-alternating sum of a sequence (y_1,...,y_k) is Sum_i (-1)^(k-i) y_i.

Examples

			The terms and corresponding compositions begin:
    0: ()
   11: (2,1,1)
   12: (1,3)
   14: (1,1,2)
  133: (5,2,1)
  138: (4,2,2)
  143: (4,1,1,1,1)
  148: (3,2,3)
  155: (3,1,2,1,1)
  158: (3,1,1,1,2)
  160: (2,6)
  168: (2,2,4)
  179: (2,1,3,1,1)
  182: (2,1,2,1,2)
  188: (2,1,1,1,3)
		

Crossrefs

These compositions are counted by A262977 up to 0's.
Except for 0, a subset of A345917.
The unreversed version is A348614.
The unreversed negative version is A349154.
The negative version is A349155.
A non-reverse unordered version is A349159, counted by A000712 up to 0's.
An unordered version is A349160, counted by A006330 up to 0's.
A003242 counts Carlitz compositions.
A011782 counts compositions.
A025047 counts alternating or wiggly compositions, complement A345192.
A034871, A097805, and A345197 count compositions by alternating sum.
A103919 counts partitions by alternating sum, reverse A344612.
A116406 counts compositions with alternating sum >=0, ranked by A345913.
A138364 counts compositions with alternating sum 0, ranked by A344619.
Statistics of standard compositions:
- The compositions themselves are the rows of A066099.
- Number of parts is given by A000120, distinct A334028.
- Sum and product of parts are given by A070939 and A124758.
- Maximum and minimum parts are given by A333766 and A333768.
- Heinz number is given by A333219.
Classes of standard compositions:
- Partitions and strict partitions are ranked by A114994 and A333256.
- Multisets and sets are ranked by A225620 and A333255.
- Strict and constant compositions are ranked by A233564 and A272919.
- Carlitz compositions are ranked by A333489, complement A348612.
- Alternating compositions are ranked by A345167, complement A345168.

Programs

  • Mathematica
    stc[n_]:=Differences[ Prepend[Join@@Position[ Reverse[IntegerDigits[n,2]],1],0]]//Reverse;
    sats[y_]:=Sum[(-1)^(i-Length[y])*y[[i]],{i,Length[y]}];
    Select[Range[0,1000],Total[stc[#]]==2*sats[stc[#]]&]

A115982 Number of planar partitions that are not corners.

Original entry on oeis.org

0, 0, 0, 1, 3, 10, 23, 54, 112, 228, 437, 826, 1499, 2685, 4688, 8079, 13668, 22875, 37738, 61676, 99672, 159742, 253681, 399962, 625741, 972756, 1502302, 2306988, 3522492, 5351239, 8088469, 12170163, 18229411, 27192571
Offset: 1

Views

Author

Alford Arnold, Feb 17 2006

Keywords

Comments

a(n) can also be approximated by considering A000094 since A000094(n) = A000041(n) - n = 0 0 0 1 2 5 8 14 21 32 ... with partial sums 0 0 0 1 3 8 16 30 51 83 ... which counts many of the initial cases. The remaining cases form 0 0 0 0 0 2 7 24 ... counting for n=6, 22/11 and 21/21.

Examples

			The planar partitions begin 1 3 6 13 24 48 ... A000219 with corners 1 3 6 12 21 38 ... A006330; therefore the present sequence begins 0 0 0 1 3 10 ...
		

Crossrefs

Formula

a(n) = A000219(n) - A006330(n)

Extensions

Edited with additional terms by Franklin T. Adams-Watters, Mar 10 2006

A288578 q-Expansion of wedge character chi^(2)(q).

Original entry on oeis.org

1, 2, 5, 9, 18, 31, 55, 91, 151, 240, 381, 587, 900, 1352, 2018, 2966, 4332, 6250, 8962, 12725, 17962, 25147, 35015, 48414, 66603, 91071, 123945, 167786, 226154, 303375, 405337, 539249, 714740, 943659, 1241605, 1627812, 2127302, 2770966, 3598567
Offset: 0

Views

Author

N. J. A. Sloane, Jul 01 2017

Keywords

Crossrefs

Cf. A006330 (chi^(0)(q)), A001523 (chi^(1)(q)).

Programs

  • Maple
    chi := proc(l,e)
        local gf,m,n,f;
        gf := 0 ;
        for m from 0 to e+1 do
            f := 1;
            for n from 1 to min(m+abs(l),e-m+1) do
                f := f/(1-q^n) ;
            end do:
            for n from 1 to min(m,e-m+1) do
                f := f/(1-q^n) ;
            end do:
            gf := gf+f*q^m ;
        end do:
        expand(gf) ;
        coeftayl(%,q=0,e) ;
    end proc:
    A288578 := proc(n)
        chi(2,n) ;
    end proc:
    for n from 0 do
        printf("%d,\n",A288578(n)) ;
    end do: # R. J. Mathar, Jul 04 2017

A110582 Triangle, read by rows, where the g.f. of diagonal n, D_n(x), is generated from the g.f. of row n-1, R_{n-1}(x), by D_n(x) = R_{n-1}(x)/(1-x)^2 for n>0, with D_0(x) = 1/(1-x)^2.

Original entry on oeis.org

1, 1, 2, 1, 2, 3, 1, 4, 3, 4, 1, 4, 7, 4, 5, 1, 6, 10, 10, 5, 6, 1, 6, 14, 16, 13, 6, 7, 1, 8, 18, 26, 22, 16, 7, 8, 1, 8, 25, 34, 38, 28, 19, 8, 9, 1, 10, 29, 52, 55, 50, 34, 22, 9, 10, 1, 10, 37, 66, 84, 76, 62, 40, 25, 10, 11, 1, 12, 44, 90, 116, 122, 97, 74, 46, 28, 11, 12
Offset: 0

Views

Author

Paul D. Hanna, Jul 29 2005

Keywords

Comments

Related to planar partitions.

Examples

			Triangle begins:
1;
1,2;
1,2,3;
1,4,3,4;
1,4,7,4,5;
1,6,10,10,5,6;
1,6,14,16,13,6,7;
1,8,18,26,22,16,7,8;
1,8,25,34,38,28,19,8,9;
1,10,29,52,55,50,34,22,9,10; ...
Row sums form A006330 (offset 1):
{1,3,6,12,21,38,63,106,170,272,422,653,...},
(planar partitions with only one row and one column).
G.f. of diagonal n, D_n(x), is generated from g.f. of
row n-1, R_{n-1}(x), by D_n(x) = R_{n-1}(x)/(1-x)^2:
D_3(x) = 1 + 4*x + 10*x^2 + 16*x^3 + 22*x^4 + ...
= (1 + 2*x + 3*x^2)/(1-x)^2 = R_2(x)/(1-x)^2;
D_4(x) = 1 + 6*x + 14*x^2 + 26*x^3 + 38*x^4 + ...
= (1+ 4*x+ 3*x^2+ 4*x^3)/(1-x)^2 = R_3(x)/(1-x)^2.
		

Crossrefs

Cf. A006330 (row sums).

Programs

  • Mathematica
    T[n_, k_] := T[n, k] = If[n < k || k < 0, 0, If[k == 0, 1, If[k == n, n + 1, Sum[T[n - k - 1, j]*(k - j + 1), {j, 0, k}]]]]; Table[T[n, k], {n, 0, 20}, {k, 0, n}] // Flatten (* G. C. Greubel, Sep 01 2017 *)
  • PARI
    T(n,k)=if(n
    				
  • PARI
    T(n,k)=local(X=x+x*O(x^n),Y=y+y*O(y^k));if(n
    				

Formula

T(n, k) = Sum_{j=0..k} T(n-k-1, j)*(k-j+1) with T(n, n) = n+1.
G.f.: A(x, y) = Sum_{j=0..n} x^j/Product_{i=1..j+1} (1-y*x^i)^2.

A116600 a(n) = A011782(n) + A000219(n) - A000712(n).

Original entry on oeis.org

1, 0, 0, 0, 1, 4, 15, 40, 103, 238, 531, 1131, 2362, 4811, 9694, 19307, 38243, 75400, 148443, 291984, 574724, 1132368, 2234617, 4416937, 8745567, 17343737, 34446090, 68500682, 136374947, 271755878, 541950747, 1081467319, 2159170372, 4312555339, 8616279482, 17219151572, 34418065540, 68805730450, 137566021077
Offset: 0

Views

Author

Alford Arnold, Feb 18 2006

Keywords

Comments

Old definition was "Counts compositions plus plane partitions less partitions into parts of two kinds".
A116600 is essentially A115981 + A115982 since A000712 = A001523 + A006330.

Examples

			a(8) = 103 because A011782(8) + A000219(8) - A000712(8) = 128 + 160 - 185.
		

Crossrefs

Programs

  • PARI
    N=66; x='x+O('x^N);
    gf011782 =(1-x)/(1-2*x);
    gf000219 = 1/prod(n=1,N, (1-x^n)^n );
    gf000712 = 1/eta(x)^2;
    Vec( gf011782 + gf000219 - gf000712 )
    \\ Joerg Arndt, Mar 25 2014

Formula

a(n) = A011782(n) + A000219(n) - A000712(n).

Extensions

Terms a(9) and beyond from Joerg Arndt, Mar 25 2014

A259100 Triangle read by rows, arising in the enumeration of corners.

Original entry on oeis.org

1, 0, 1, 0, 2, 1, 0, 3, 2, 1, 0, 4, 5, 2, 1, 0, 5, 8, 5, 2, 1, 0, 6, 14, 10, 5, 2, 1, 0, 7, 20, 18, 10, 5, 2, 1, 0, 8, 30, 30, 20, 10, 5, 2, 1
Offset: 0

Views

Author

N. J. A. Sloane, Jun 22 2015

Keywords

Examples

			Triangle begins:
  1;
  0,  1;
  0,  2,  1;
  0,  3,  2,  1;
  0,  4,  5,  2,  1;
  0,  5,  8,  5,  2,  1;
  0,  6, 14, 10,  5,  2,  1;
  0,  7, 20, 18, 10,  5,  2,  1;
  0,  8, 30, 30, 20, 10,  5,  2,  1;
  ...
		

Crossrefs

Row sums = A006330.

Formula

Kreweras gives a recurrence on page 281.

A259101 Square array read by antidiagonals arising in the enumeration of corners.

Original entry on oeis.org

1, 2, 2, 5, 16, 5, 14, 91, 91, 14, 42, 456, 936, 456, 42, 132, 2145, 7425, 7425, 2145, 132, 429, 9724, 50765, 85800, 50765, 9724, 429, 1430, 43043, 315315, 805805, 805805, 315315, 43043, 1430, 4862, 187408, 1831648, 6584032, 9962680, 6584032, 1831648, 187408, 4862, 16796, 806208, 10127988, 48674808, 103698504, 103698504, 48674808, 10127988, 806208, 16796
Offset: 0

Views

Author

N. J. A. Sloane, Jun 22 2015

Keywords

Comments

See Kreweras (1979) for precise definition.

Examples

			The first few antidiagonals are:
    1,
    2,    2,
    5,   16,    5,
   14,   91,   91,   14,
   42,  456,  936,  456,   42,
  132, 2145, 7425, 7425, 2145, 132,
  ...
		

Crossrefs

The first row and column of the array are the Catalan numbers A000108.
The second row and column are A214824.

Programs

  • Mathematica
    a[x_, y_] := (2(2x+2y+1)!(x^2+3x*y+y^2+4x+4y+3)) / (x!(x+1)!y!(y+1)!(x+y+1)(x+y+2)(x+y+3));
    Table[Table[a[x-y, y], {y, 0, x}] // Reverse, {x, 0, 9}] // Flatten (* Jean-François Alcover, Aug 11 2017 *)

Formula

Kreweras gives an explicit formula for the general term (see bottom display on page 291).

Extensions

More terms from Jean-François Alcover, Aug 11 2017

A356367 Number of plane partitions of n having exactly one row and one column, each of equal length.

Original entry on oeis.org

1, 1, 1, 2, 2, 5, 6, 11, 16, 26, 36, 58, 81, 122, 172, 251, 350, 502, 692, 972, 1332, 1842, 2499, 3414, 4592, 6200, 8277, 11064, 14656, 19424, 25544, 33584, 43880, 57274, 74362, 96429, 124468, 160422, 205942, 263938, 337083, 429768
Offset: 0

Views

Author

Jeremy Lovejoy, Oct 16 2022

Keywords

Comments

The empty plane partition of 0 contributes an initial term equal to 1.
Also equal to the number of unimodal compositions of n+1 where the peak appears exactly once and the number of parts to the left of the peak is equal to the number of parts to the right of the peak.

Examples

			For n = 7 the valid unimodal compositions of n+1=8 are (8), (1,6,1), (1,5,2), (2,5,1), (3,4,1), (1,4,3), (2,4,2), (1,1,4,1,1), (1,1,3,2,1), (1,2,3,1,1) and (1,1,1,2,1,1,1), and so a(7) = 11.
		

Crossrefs

Programs

  • Mathematica
    nmax = 50; CoefficientList[Series[1 + 1/Product[(1 - x^k)^2, {k, 1, nmax}] * Sum[(-1)^(k + r + 1) * x^(k*(k + 1)/2 + r*(r + 1)/2 + 2*k*r)*(1 - x^r), {r, 0, nmax}, {k, 0, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Apr 28 2023 *)

Formula

G.f.: 1 + (1/Product_{n>=1}(1-x^n)^2)*Sum_{r,n>=0}(-1)^(n+r+1)*x^(n*(n+1)/2 + r*(r+1)/2 + 2*n*r)*(1-x^r).
Previous Showing 41-48 of 48 results.