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 21-26 of 26 results.

A301739 The number of trees with 4 nodes labeled by positive integers, where each tree's label sum is n.

Original entry on oeis.org

2, 4, 10, 17, 30, 44, 67, 91, 126, 163, 213, 265, 333, 403, 491, 582, 693, 807, 944, 1084, 1249, 1418, 1614, 1814, 2044, 2278, 2544, 2815, 3120, 3430, 3777, 4129, 4520, 4917, 5355, 5799, 6287, 6781, 7321, 7868, 8463, 9065, 9718, 10378, 11091, 11812, 12588, 13372, 14214, 15064
Offset: 4

Views

Author

R. J. Mathar, Mar 26 2018

Keywords

Comments

Computed by the sum over the A000055(4)=2 shapes of the trees: the linear graph of the n-Butane, and the star graph of (1)-Methyl-Propane.

Examples

			a(4)=2 because there is a linear tree with all labels equal 1 and the star tree with all labels equal to 1.
		

Crossrefs

4th column of A303841.

Programs

  • Maple
    x^4*(2+2*x+2*x^2+x^3+x^4)/(1+x)^2/(x-1)^4/(1+x+x^2) ;
    taylor(%,x=0,80) ;
    gfun[seriestolist](%) ;

Formula

a(n) = A005993(n-4)+A000601(n-4).
G.f.: x^4*(2+2*x+2*x^2+x^3+x^4)/((1+x)^2*(x-1)^4*(1+x+x^2) ).

A099770 Expansion of 1/((1-x)*(1-x^2)*(1-x^4)*(1-x^6)).

Original entry on oeis.org

1, 1, 2, 2, 4, 4, 7, 7, 11, 11, 16, 16, 23, 23, 31, 31, 41, 41, 53, 53, 67, 67, 83, 83, 102, 102, 123, 123, 147, 147, 174, 174, 204, 204, 237, 237, 274, 274, 314, 314, 358, 358, 406, 406, 458, 458, 514, 514, 575, 575, 640, 640, 710, 710, 785, 785, 865, 865, 950, 950, 1041, 1041
Offset: 0

Views

Author

G. Nebe (nebe(AT)math.rwth-aachen.de), Nov 10 2004

Keywords

Comments

Molien series for symmetrized weight enumerators of Hermitian self-dual codes over the Galois ring GR(4,2).
Number of partitions of n into parts 1, 2, 4, and 6. - Joerg Arndt, May 05 2014
a(n) is equal to the number of partitions of degree at most n+6 of length 3 with even entries. - John M. Campbell, Jan 20 2016

Examples

			From _John M. Campbell_, Jan 20 2016: (Start)
Letting n=6, a(n) = 7 is equal to the number of partitions of n into parts 1, 2, 4, and 6, as illustrated below, and a(n) is equal to the number of partitions of degree at most n+6 of length 3 with even entries, as illustrated below. The arrows below illustrate a natural bijection between the set of partitions of the former form and the set of partitions of the latter form.
(2, 2, 2) <-> (1, 1, 1, 1, 1, 1)
(4, 2, 2) <-> (2, 1, 1, 1, 1)
(6, 2, 2) <-> (4, 1, 1)
(4, 4, 2) <-> (2, 2, 1, 1)
(8, 2, 2) <-> (6)
(6, 4, 2) <-> (4, 2)
(4, 4, 4) <-> (2, 2, 2)
(End)
		

Crossrefs

Programs

  • GAP
    a:=[1,1,2,2,4,4,7,7,11,11,16,16,23];; for n in [14..65] do a[n]:= a[n-1]+a[n-2]-a[n-3]+a[n-4]-a[n-5]-a[n-8]+a[n-9]-a[n-10]+a[n-11]+a[n-12] -a[n-13]; od; a; # G. C. Greubel, Sep 04 2019
  • Magma
    R:=PowerSeriesRing(Integers(), 65); Coefficients(R!( 1/((1-x)*(1-x^2)*(1-x^4)*(1-x^6)) )); // G. C. Greubel, Sep 04 2019
    
  • Maple
    seq(coeff(series(1/((1-x)*(1-x^2)*(1-x^4)*(1-x^6)), x, n+1), x, n), n = 0 .. 65); # G. C. Greubel, Sep 04 2019
  • Mathematica
    CoefficientList[Series[1/((1-x)*(1-x^2)*(1-x^4)*(1-x^6)), {x, 0, 65}], x] (* G. C. Greubel, Sep 04 2019 *)
  • PARI
    Vec(1/((1-x)*(1-x^2)*(1-x^4)*(1-x^6)) + O(x^80)) \\ Michel Marcus, Jan 21 2016
    
  • Sage
    def A099770_list(prec):
        P. = PowerSeriesRing(ZZ, prec)
        return P(1/((1-x)*(1-x^2)*(1-x^4)*(1-x^6))).list()
    A099770_list(65) # G. C. Greubel, Sep 04 2019
    

Formula

a(n) ~ 1/288*n^3. - Ralf Stephan, Apr 29 2014
a(n) = (2*n^3 +39*n^2 +241*n +372 +3*(n^2 +13*n +40) * (-1)^n -84*(-1)^((2*n +3 +(-1)^n)/4) -192*floor(((2*n +9 +(-1)^n-6*(-1)^((2*n+3+(-1)^n)/4))/24)))/576. - Luce ETIENNE, May 05 2014
a(n) = A000601(A004526(n)). - Hoang Xuan Thanh, Jun 21 2025

A259324 Infinite square array read by antidiagonals: T(n,k) = number of ways of partitioning numbers <= n into k parts (n >= 0, k >= 1).

Original entry on oeis.org

1, 1, 2, 1, 2, 3, 1, 2, 4, 4, 1, 2, 4, 6, 5, 1, 2, 4, 7, 9, 6, 1, 2, 4, 7, 11, 12, 7, 1, 2, 4, 7, 12, 16, 16, 8, 1, 2, 4, 7, 12, 18, 23, 20, 9, 1, 2, 4, 7, 12, 19, 27, 31, 25, 10, 1, 2, 4, 7, 12, 19, 29, 38, 41, 30, 11, 1, 2, 4, 7, 12, 19, 30, 42, 53, 53, 36, 12, 1, 2, 4, 7, 12, 19, 30, 44, 60, 71, 67, 42, 13, 1, 2, 4, 7, 12, 19, 30, 45, 64, 83, 94, 83, 49, 14, 1, 2
Offset: 0

Views

Author

N. J. A. Sloane, Jun 24 2015

Keywords

Examples

			The first few antidiagonals are:
1,
1,2,
1,2,3,
1,2,4,4,
1,2,4,6,5,
1,2,4,7,9,6,
1,2,4,7,11,12,7,
1,2,4,7,12,16,16,8,
...
		

Crossrefs

Columns give A002620, A000601, A002621, A002622.
Cf. A137679.

Programs

  • Maple
    A259324 := proc(u,m)
        option remember;
        if u = 0 then
            1;
        elif u < 0 then
            0;
        elif m = 1 then
            u+1 ;
        else
            procname(u,m-1)+procname(u-m,m) ;
        end if;
    end proc:
    for d from 1 to 15 do
        for m from d to 1 by -1 do
            printf("%d,",A259324(d-m,m)) ;
        end do:
    end do: # R. J. Mathar, Jul 14 2015
  • Mathematica
    T[0, ] = 1; T[u /; u > 0, m_ /; m > 1] := T[u, m] = T[u, m - 1] + T[u - m, m]; T[u_, 1] := u + 1; T[, ] = 0;
    Table[T[u - m, m], {u, 0, 14}, {m, u, 1, -1}] // Flatten (* Jean-François Alcover, Apr 05 2020 *)

Formula

T(u,m) = T(u,m-1)+T(u-m,m), with initial conditions T(0,m)=1, T(m,1)=u+1.

A282044 Reduced Kronecker coefficients for the case a=2, b=3, i=4.

Original entry on oeis.org

0, 0, 0, 0, 1, 2, 5, 9, 16, 24, 37, 51, 71, 93
Offset: 0

Views

Author

N. J. A. Sloane, Feb 21 2017

Keywords

Comments

Table 3 of Colmenarejo (2016) shows this sequence as the missing member of the family A266769, A000601, A006918, A014126, A282044, A175287.
It would be nice to have a g.f.

Crossrefs

Formula

Conjectured g.f.: x^4*(1+x^2)/(1-2*x+x^3+3*x^5-4*x^6). - Jean-François Alcover, Feb 18 2019.

A164679 Convolve A001399 with sequences which map to 2,3,5,7,11,13,17... A000040 then, by bending when needed, summarize the results in a triangular array.

Original entry on oeis.org

1, 2, 1, 5, 4, 2, 10, 9, 7, 3, 19, 18, 16, 11, 4, 33, 32, 30, 25, 16, 5, 57
Offset: 1

Views

Author

Alford Arnold, Sep 05 2009

Keywords

Comments

Apparently the terms can be constructed by fixing the generating function of the diagonal g_0(x) = 1/(1-x)/(1-x^2)/(1-x^3), A001399, and deriving the generating function of the i-th subdiagonal by g_i(x) = g_{i-1}(x)/(1-x^i), i>=1. - R. J. Mathar, May 17 2016

Examples

			1;
2, 1;
5, 4, 2;
10, 9, 7, 3;
19, 18, 16, 11, 4;
33, 32, 30, 25, 16, 5;
57
		

Crossrefs

Cf. A000098 (first column), A164678 (a similar triangle). Diagonals are A001399, A000601, A097701, A117485, ...

A259325 Infinite square array T(n,k) read by antidiagonals, defined by T(n,k) = T(n,k-1)+T(n-k,k), T(0,k)=1 (n >= 0, k >= 1).

Original entry on oeis.org

1, 1, 3, 1, 3, 7, 1, 3, 8, 13, 1, 3, 8, 16, 22, 1, 3, 8, 17, 30, 34, 1, 3, 8, 17, 33, 50, 50, 1, 3, 8, 17, 34, 58, 80, 70, 1, 3, 8, 17, 34, 61, 97, 120, 95
Offset: 0

Views

Author

N. J. A. Sloane, Jun 24 2015

Keywords

Examples

			The first few antidiagonals are:
1
1,3,
1,3,7
1,3,8,13
1,3,8,16,22
1,3,8,17,30,34
1,3,8,17,33,50,50
1,3,8,17,34,58,80,70
1,3,8,17,34,61,97,120,95
...
		

Crossrefs

Columns give A002623, A002624, A002625, A002626.
Previous Showing 21-26 of 26 results.