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 21-30 of 36 results. Next

A140953 Expansion of 1/((1-x^2)*(1-x^3)*(1-x^5)*(1-x^7)*(1-x^11)*(1-x^13)).

Original entry on oeis.org

1, 0, 1, 1, 1, 2, 2, 3, 3, 4, 5, 6, 7, 9, 10, 12, 14, 16, 19, 21, 25, 28, 32, 36, 41, 46, 52, 58, 65, 72, 80, 89, 98, 109, 119, 132, 144, 158, 173, 189, 206, 224, 244, 264, 287, 310, 336, 362, 391, 421, 453, 487, 523, 561, 601, 644, 688, 736, 785, 838, 893
Offset: 0

Views

Author

Alois P. Heinz, Jul 25 2008

Keywords

Comments

Number of partitions of n into the first 6 primes. [Corrected by Harvey P. Dale, Dec 05 2022]

Crossrefs

Programs

  • Maple
    M := Matrix(41, (i,j)-> if (i=j-1) or (j=1 and member(i, [2, 3, 11, 19, 20, 21, 22, 30, 38, 39])) then 1 elif j=1 and member(i, [8, 9, 16, 17, 24, 25, 32, 33, 41]) then -1 else 0 fi):
    a:= n -> (M^(n))[1,1]:
    seq(a(n), n=0..50);
  • Mathematica
    CoefficientList[Series[1/Times@@Table[1-x^p,{p,Prime[Range[6]]}],{x,0,60}],x] (* or *) LinearRecurrence[{0,1,1,0,0,0,0,-1,-1,0,1,0,0,0,0,-1,-1,0,1,1,1,1,0,-1,-1,0,0,0,0,1,0,-1,-1,0,0,0,0,1,1,0,-1},{1,0,1,1,1,2,2,3,3,4,5,6,7,9,10,12,14,16,19,21,25,28,32,36,41,46,52,58,65,72,80,89,98,109,119,132,144,158,173,189,206},70] (* Harvey P. Dale, Dec 05 2022 *)

A246720 Number A(n,k) of partitions of n into parts of the k-th list of distinct parts in the order given by A246688; square array A(n,k), n>=0, k>=0, read by antidiagonals.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 0, 1, 0, 1, 1, 1, 1, 0, 1, 0, 2, 0, 1, 0, 1, 1, 0, 2, 1, 1, 0, 1, 0, 1, 1, 3, 0, 1, 0, 1, 1, 0, 2, 0, 3, 1, 1, 0, 1, 0, 1, 0, 2, 0, 4, 0, 1, 0, 1, 0, 1, 1, 1, 2, 1, 4, 1, 1, 0, 1, 1, 0, 1, 2, 0, 3, 0, 5, 0, 1, 0, 1, 1, 2, 0, 1, 2, 0, 3, 0, 5, 1, 1, 0
Offset: 0

Views

Author

Alois P. Heinz, Sep 02 2014

Keywords

Comments

The first lists of distinct parts in the order given by A246688 are: 0:[], 1:[1], 2:[2], 3:[1,2], 4:[3], 5:[1,3], 6:[4], 7:[1,4], 8:[2,3], 9:[5], 10:[1,2,3], 11:[1,5], 12:[2,4], 13:[6], 14:[1,2,4], 15:[1,6], 16:[2,5], 17:[3,4], 18:[7], 19:[1,2,5], 20:[1,3,4], ... .

Examples

			Square array A(n,k) begins:
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1,  1, ...
  0, 1, 0, 1, 0, 1, 0, 1, 0, 0,  1, 1, 0, 0,  1, ...
  0, 1, 1, 2, 0, 1, 0, 1, 1, 0,  2, 1, 1, 0,  2, ...
  0, 1, 0, 2, 1, 2, 0, 1, 1, 0,  3, 1, 0, 0,  2, ...
  0, 1, 1, 3, 0, 2, 1, 2, 1, 0,  4, 1, 2, 0,  4, ...
  0, 1, 0, 3, 0, 2, 0, 2, 1, 1,  5, 2, 0, 0,  4, ...
  0, 1, 1, 4, 1, 3, 0, 2, 2, 0,  7, 2, 2, 1,  6, ...
  0, 1, 0, 4, 0, 3, 0, 2, 1, 0,  8, 2, 0, 0,  6, ...
  0, 1, 1, 5, 0, 3, 1, 3, 2, 0, 10, 2, 3, 0,  9, ...
  0, 1, 0, 5, 1, 4, 0, 3, 2, 0, 12, 2, 0, 0,  9, ...
  0, 1, 1, 6, 0, 4, 0, 3, 2, 1, 14, 3, 3, 0, 12, ...
		

Crossrefs

Main diagonal gives A246721.
Cf. A246688, A246690 (the same for compositions).

Programs

  • Maple
    b:= proc(n, i) b(n, i):= `if`(n=0, [[]], `if`(i>n, [],
          [map(x->[i, x[]], b(n-i, i+1))[], b(n, i+1)[]]))
        end:
    f:= proc() local i, l; i, l:=0, [];
          proc(n) while n>=nops(l)
            do l:=[l[], b(i, 1)[]]; i:=i+1 od; l[n+1]
          end
        end():
    g:= proc(n, l) option remember; `if`(n=0, 1, `if`(l=[], 0,
          add(g(n-l[-1]*j, subsop(-1=NULL, l)), j=0..n/l[-1])))
        end:
    A:= (n, k)-> g(n, f(k)):
    seq(seq(A(n, d-n), n=0..d), d=0..16);
  • Mathematica
    b[n_, i_] := b[n, i] = If[n == 0, {{}}, If[i > n, {}, Join[Prepend[#, i]& /@ b[n - i, i + 1], b[n, i + 1]]]];
    f = Module[{i = 0, l = {}}, Function[n, While[ n >= Length[l], l = Join[l, b[i, 1]]; i++ ]; l[[n + 1]]]];
    g[n_, l_] := g[n, l] = If[n == 0, 1, If[l == {}, 0, Sum[g[n - l[[-1]] j, ReplacePart[l, -1 -> Nothing]], {j, 0, n/l[[-1]]}]]];
    A[n_, k_] := g[n, f[k]];
    Table[Table[A[n, d - n], {n, 0, d}], {d, 0, 16}] // Flatten (* Jean-François Alcover, Dec 07 2020, after Alois P. Heinz *)

A266779 Molien series for invariants of finite Coxeter group A_10.

Original entry on oeis.org

1, 0, 1, 1, 2, 2, 4, 4, 7, 8, 12, 14, 20, 23, 32, 38, 50, 59, 77, 90, 115, 135, 168, 197, 243, 283, 344, 401, 481, 558, 665, 767, 906, 1043, 1221, 1401, 1631, 1862, 2155, 2454, 2823, 3203, 3668, 4147, 4727, 5330, 6047, 6798, 7685, 8612, 9700, 10843, 12168, 13566, 15178, 16877, 18825, 20884, 23226, 25707, 28517, 31489, 34842, 38396
Offset: 0

Views

Author

N. J. A. Sloane, Jan 11 2016

Keywords

Comments

The Molien series for the finite Coxeter group of type A_k (k >= 1) has g.f. = 1/Product_{i=2..k+1} (1 - x^i).
Note that this is the root system A_k, not the alternating group Alt_k.

References

  • J. E. Humphreys, Reflection Groups and Coxeter Groups, Cambridge, 1990. See Table 3.1, page 59.

Crossrefs

Molien series for finite Coxeter groups A_1 through A_12 are A059841, A103221, A266755, A008667, A037145, A001996, and A266776-A266781.

Programs

  • Magma
    R:=PowerSeriesRing(Integers(), 70); Coefficients(R!( 1/(&*[1-x^j: j in [2..11]]) )); // G. C. Greubel, Feb 03 2020
    
  • Maple
    seq(coeff(series(1/mul(1-x^j, j=2..11), x, n+1), x, n), n = 0..70); # G. C. Greubel, Feb 03 2020
  • Mathematica
    CoefficientList[Series[1/Product[1-x^j, {j,2,11}], {x,0,70}], x] (* G. C. Greubel, Feb 03 2020 *)
  • PARI
    Vec( 1/prod(j=2,11,1-x^j) +O('x^70)) \\ G. C. Greubel, Feb 03 2020
    
  • Sage
    def A266779_list(prec):
        P. = PowerSeriesRing(ZZ, prec)
        return P( 1/product(1-x^j for j in (2..11))).list()
    A266779_list(70) # G. C. Greubel, Feb 03 2020

Formula

G.f.: 1/((1-t^2)*(1-t^3)*(1-t^4)*(1-t^5)*(1-t^6)*(1-t^7)*(1-t^8)*(1-t^9)*(1-t^10)*(1-t^11)).

A266780 Molien series for invariants of finite Coxeter group A_11.

Original entry on oeis.org

1, 0, 1, 1, 2, 2, 4, 4, 7, 8, 12, 14, 21, 23, 33, 39, 52, 61, 81, 94, 122, 143, 180, 211, 264, 306, 377, 440, 533, 619, 746, 861, 1028, 1186, 1401, 1612, 1895, 2168, 2532, 2894, 3356, 3822, 4414, 5008, 5755, 6516, 7448, 8410, 9580, 10780, 12232, 13737, 15524, 17388, 19592, 21885, 24580, 27400, 30674, 34117, 38097, 42269, 47074, 52133
Offset: 0

Views

Author

N. J. A. Sloane, Jan 11 2016

Keywords

Comments

The Molien series for the finite Coxeter group of type A_k (k >= 1) has g.f. = 1/Product_{i=2..k+1} (1 - x^i).
Note that this is the root system A_k, not the alternating group Alt_k.

References

  • J. E. Humphreys, Reflection Groups and Coxeter Groups, Cambridge, 1990. See Table 3.1, page 59.

Crossrefs

Molien series for finite Coxeter groups A_1 through A_12 are A059841, A103221, A266755, A008667, A037145, A001996, and A266776-A266781.

Programs

  • Magma
    R:=PowerSeriesRing(Integers(), 70); Coefficients(R!( 1/(&*[1-x^j: j in [2..12]]) )); // G. C. Greubel, Feb 04 2020
    
  • Maple
    S:=series(1/mul(1-x^j, j=2..12)), x, 75):
    seq(coeff(S, x, j), j=0..70); # G. C. Greubel, Feb 04 2020
  • Mathematica
    CoefficientList[Series[1/Times@@(1-t^Range[2,12]),{t,0,70}],t] (* Harvey P. Dale, Jun 20 2017 *)
  • PARI
    Vec( 1/prod(j=2,12, 1-x^j) +O('x^70) ) \\ G. C. Greubel, Feb 04 2020
    
  • Sage
    def A266780_list(prec):
        P. = PowerSeriesRing(ZZ, prec)
        return P( 1/prod(1-x^j for j in (2..12)) ).list()
    A266780_list(70) # G. C. Greubel, Feb 04 2020

Formula

G.f.: 1/((1-t^2)*(1-t^3)*(1-t^4)*(1-t^5)*(1-t^6)*(1-t^7)*(1-t^8)*(1-t^9)*(1-t^10)*(1-t^11)*(1-t^12)).

A376782 Triangle read by rows: T(n,m) is the number of unlabeled graphs with n vertices having m minimum forbidden subgraphs, n >= 1, 1 <= m <= A371162(n).

Original entry on oeis.org

1, 1, 1, 1, 3, 1, 4, 4, 2, 1, 4, 8, 13, 8, 1, 4, 5, 7, 20, 34, 31, 28, 12, 8, 5, 0, 1, 1, 4, 5, 13, 26, 33, 43, 59, 50, 62, 58, 60, 64, 67, 63, 70, 68, 65, 61, 60, 31, 28, 16, 8, 13, 4, 4, 4, 0, 2, 1, 0, 1, 1, 4, 6, 9, 21, 34, 39, 71, 74, 77, 99, 118, 124, 107, 129
Offset: 1

Views

Author

Max Alekseyev, Oct 03 2024

Keywords

Examples

			Triangle starts with
n = 1: 1
n = 2: 1 1
n = 3: 1 3
n = 4: 1 4 4  2
n = 5: 1 4 8 13  8
n = 6: 1 4 5  7 20 34 31 28 12 8 5 0 1
...
		

Crossrefs

Cf. A000088 (row sums), A371162 (row lengths), A000012 (column m=1), A113311 (column m=2).

A081753 a(n) = floor(n/12) if n == 2 (mod 12); a(n) = floor(n/12) + 1 otherwise.

Original entry on oeis.org

1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 8, 9, 9, 9, 9, 9, 9
Offset: 0

Views

Author

Benoit Cloitre, Apr 08 2003

Keywords

Comments

a(2n) = dimension of M(2n), where M(2n) denotes the complex vector space of modular forms of weight 2n for the group : PSL2(Z). dimension of M(2n+1) = 0.
See A103221(n) for the dimension of M(2n). The Apostol reference, p. 119, eq. (9) uses even k. - Wolfdieter Lang, Sep 16 2016
The space of modular forms is generated by E_4 (A004009) and E_6 (A013973) both of even weight. This is why the space of modular forms of odd weight is trivial. - Michael Somos, Dec 11 2018

Examples

			G.f. = 1 + x + x^3 + x^4 + x^5 + x^6 + x^7 + x^8 + x^9 + x^10 + x^11 + 2*x^12 + ... - _Michael Somos_, Dec 11 2018
		

References

  • Apostol, Tom M., Modular Functions and Dirichlet Series in Number Theory, second edition, Springer, 1990.
  • Yves Hellegouarch, "Invitation aux mathématiques de Fermat-Wiles", Dunod, 2ème édition, p. 285

Crossrefs

Programs

  • Maple
    seq(floor(n/12)+1-charfcn[0](n-2 mod 12), n=0..100); # Robert Israel, Sep 16 2016
  • Mathematica
    Table[If[Mod[n, 12] == 2, Floor[n/12], Floor[n/12] + 1], {n, 0, 120}] (* or *)
    CoefficientList[Series[(1 - x^2 + x^3)/(1 - x - x^12 + x^13), {x, 0, 120}], x] (* Michael De Vlieger, Sep 19 2016 *)
    a[ n_] := Quotient[n, 12] + Boole[Mod[n, 12] != 2]; (* Michael Somos, Dec 11 2018 *)
  • PARI
    a(k) = if(k%12-2, floor(k/12)+1, floor(k/12))
    
  • PARI
    {a(n) = n\12 + (n%12!=2)}; /* Michael Somos, Dec 11 2018 */

Formula

a(n) = floor(n/12) if n == 2 (mod 12); a(n) = floor(n/12) + 1 otherwise.
G.f.: (1-x^2+x^3)/(1-x-x^12+x^13). - Robert Israel, Sep 16 2016
a(2*n) = A008615(n+2), a(2*n+1) = A097992(n). - Michael Somos, Dec 11 2018

A307018 Total number of parts of size 3 in the partitions of n into parts of size 2 and 3.

Original entry on oeis.org

0, 0, 0, 1, 0, 1, 2, 1, 2, 4, 2, 4, 6, 4, 6, 9, 6, 9, 12, 9, 12, 16, 12, 16, 20, 16, 20, 25, 20, 25, 30, 25, 30, 36, 30, 36, 42, 36, 42, 49, 42, 49, 56, 49, 56, 64, 56, 64, 72, 64, 72, 81, 72, 81, 90, 81, 90, 100, 90, 100, 110, 100, 110, 121, 110, 121, 132
Offset: 0

Views

Author

Andrew Ivashenko, Mar 19 2019

Keywords

Crossrefs

Programs

  • GAP
    a:=[0,0,0,1,0,1,2,1];; for n in [9..80] do a[n]:=a[n-2]+2*a[n-3] -2*a[n-5]-a[n-6]+a[n-8]; od; a; # G. C. Greubel, Apr 03 2019
  • Magma
    R:=PowerSeriesRing(Integers(), 80); [0,0,0] cat Coefficients(R!( x^3/((1-x^2)*(1-x^3)^2) )); // G. C. Greubel, Apr 03 2019
    
  • Mathematica
    LinearRecurrence[{0,1,2,0,-2,-1,0,1}, {0,0,0,1,0,1,2,1}, 80] (* G. C. Greubel, Apr 03 2019 *)
    Table[(6n(2+n)-5-27(-1)^n+8(4+3n)Cos[2n Pi/3]-8Sqrt[3]n Sin[2n Pi/3])/216,{n,0,66}] (* Stefano Spezia, Apr 21 2022 *)
  • PARI
    my(x='x+O('x^80)); concat([0,0,0], Vec(x^3/((1-x^2)*(1-x^3)^2))) \\ G. C. Greubel, Apr 03 2019
    
  • Sage
    (x^3/((1-x^2)*(1-x^3)^2)).series(x, 80).coefficients(x, sparse=False) # G. C. Greubel, Apr 03 2019
    

Formula

a(n+2) = A321202(n) - A114209(n+1).
a(3n+1) = A002620(n+2).
a(3n+2) = A002620(n+1).
a(3n+3) = A002620(n+2).
G.f.: x^3/((1+x)*(1+x+x^2)^2*(1-x)^3). - Alois P. Heinz, Mar 19 2019
a(n) = a(n-2) + 2*a(n-3) - 2*a(n-5) - a(n-6) + a(n-8). - G. C. Greubel, Apr 03 2019
a(n) = (6*n*(2 + n) + 8*(4 + 3*n)*cos(2*n*Pi/3) - 8*sqrt(3)*n*sin(2*n*Pi/3) - 5 - 27*(-1)^n)/216. - Stefano Spezia, Apr 21 2022
From Ridouane Oudra, Nov 24 2024: (Start)
a(n) = (7*n/2 - 7*n^2/2 - 9*floor(n/2) + (6*n+4)*floor(2*n/3) + 4*floor(n/3))/18.
a(n) = A008133(n) - A069905(n-1).
a(n) = A002620(A008611(n)). (End)

Extensions

More terms from Alois P. Heinz, Mar 19 2019

A376780 Triangular table read by rows: T(n,k) is the minimum number of minimal forbidden subgraphs of a graph with n vertices and k edges, n >= 1, 0 <= k <= n*(n-1)/2.

Original entry on oeis.org

1, 2, 1, 2, 2, 2, 1, 2, 3, 2, 3, 2, 2, 1, 2, 3, 2, 3, 3, 4, 3, 3, 2, 2, 1, 2, 3, 3, 2, 4, 3, 4, 5, 5, 4, 5, 5, 4, 2, 2, 1, 2, 3, 3, 2, 4, 4, 3, 4, 5, 4, 5, 5, 7, 6, 6, 5, 5, 4, 4, 2, 2, 1, 2, 3, 3, 3, 2, 4, 4, 3, 5, 6, 5, 6, 5, 5, 7, 6, 7, 10, 9, 9, 9, 8, 10, 5, 5, 4, 2, 2, 1
Offset: 1

Views

Author

Max Alekseyev, Oct 03 2024

Keywords

Examples

			Table starts with
n = 1: 1
n = 2: 2, 1
n = 3: 2, 2, 2, 1
n = 4: 2, 3, 2, 3, 2, 2, 1
...
		

Crossrefs

A376781 Triangular table read by rows: T(n,k) is the maximum number of minimal forbidden subgraphs of a graph with n vertices and k edges, n >= 1, 0 <= k <= n*(n-1)/2.

Original entry on oeis.org

1, 2, 1, 2, 2, 2, 1, 2, 3, 4, 4, 3, 2, 1, 2, 3, 4, 5, 5, 5, 5, 4, 3, 2, 1, 2, 3, 4, 6, 8, 8, 9, 13, 11, 11, 9, 6, 5, 3, 2, 1, 2, 3, 4, 6, 8, 8, 11, 16, 20, 23, 28, 31, 30, 33, 24, 22, 15, 10, 7, 3, 2, 1, 2, 3, 4, 6, 8, 9, 14, 21, 24, 31, 41, 57, 78, 86, 106, 123, 134, 149, 143, 138, 133, 75, 46, 37, 18, 11, 3, 2, 1
Offset: 1

Views

Author

Max Alekseyev, Oct 03 2024

Keywords

Examples

			Table starts with
n = 1: 1
n = 2: 2, 1
n = 3: 2, 2, 2, 1
n = 4: 2, 3, 4, 4, 3, 2, 1
...
		

Crossrefs

Cf. A371162 (row maximums).

A154950 Riordan array (1/(1-x^4), x(1+x)/(1+x^2)).

Original entry on oeis.org

1, 0, 1, 0, 1, 1, 0, -1, 2, 1, 1, -1, -1, 3, 1, 0, 2, -4, 0, 4, 1, 0, 2, 2, -8, 2, 5, 1, 0, -2, 8, -2, -12, 5, 6, 1, 1, -2, -2, 18, -12, -15, 9, 7, 1, 0, 3, -12, 8, 28, -29, -16, 14, 8, 1, 0, 3, 3, -32, 38, 31, -53, -14, 20, 9, 1
Offset: 0

Views

Author

Paul Barry, Jan 17 2009

Keywords

Comments

Row sums are A008619. Diagonal sums are A103221. Equal to A154948 times inverse of A007318.

Examples

			Triangle begins
1,
0, 1,
0, 1, 1,
0, -1, 2, 1,
1, -1, -1, 3, 1,
0, 2, -4, 0, 4, 1,
0, 2, 2, -8, 2, 5, 1,
0, -2, 8, -2, -12, 5, 6, 1,
1, -2, -2, 18, -12, -15, 9, 7, 1
		

Formula

Triangle T(n,k)=sum{i=0..n, sum{j=0..n+1, C(n+1-j,i+1)*C(i-1,j)}*(-1)^(i-k)*C(i,k)}.
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