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.

A133132 Number of surjections from an n-element set to a ten-element set.

Original entry on oeis.org

3628800, 199584000, 6187104000, 142702560000, 2731586457600, 45950224320000, 703098107712000, 10009442963520000, 134672620008326400, 1732015476199008000, 21473732319740064000, 258323865658578720000
Offset: 10

Views

Author

Mohamed Bouhamida, Dec 16 2007

Keywords

Crossrefs

Programs

  • Magma
    [10^n-10*9^n+45*8^n-120*7^n+210*6^n-252*5^n+210*4^n-120*3^n+45*2^n-10: n in [10..30]]; // Vincenzo Librandi, Apr 11 2012
  • Mathematica
    With[{nn=30},Drop[CoefficientList[Series[(Exp[x]-1)^10,{x,0,nn}],x] Range[0,nn]!,10]] (* Harvey P. Dale, Sep 01 2016 *)
  • PARI
    sum(k=1,10,(-1)^(10-k)*binomial(10,k)*k^n)
    

Formula

a(n) = 10^n-10*9^n+45*8^n-120*7^n+210*6^n-252*5^n+210*4^n-120*3^n+45*2^n-10.
a(n) = A049435(n) * 10!. - Max Alekseyev, Nov 13 2009
G.f.: 3628800*x^10/((x-1)*(2*x-1)*(3*x-1)*(4*x-1)*(5*x-1)*(6*x-1)*(7*x-1)*(8*x-1)*(9*x-1)*(10*x-1)). - Colin Barker, Oct 25 2012
E.g.f.: (exp(x)-1)^10. - Alois P. Heinz, May 17 2016

Extensions

More terms from Max Alekseyev, Nov 13 2009
Formula corrected by Charles R Greathouse IV, Mar 07 2010

A133360 Number of surjections from an n-element set to a nine-element set.

Original entry on oeis.org

362880, 16329600, 419126400, 8083152000, 130456085760, 1863435974400, 24359586451200, 297846188640000, 3457819037312640, 38528927611574400, 415357755774998400, 4358654246117808000, 44733116259693227520
Offset: 9

Views

Author

Mohamed Bouhamida, Dec 21 2007

Keywords

Crossrefs

Formula

a(n) = Sum_{k=1..9} (-1)^(9-k)*binomial(9,k)*k^n.
a(n) = A049447(n) * 9!. - Max Alekseyev, Nov 12 2009
G.f.: -362880*x^9/((x-1)*(2*x-1)*(3*x-1)*(4*x-1)*(5*x-1)*(6*x-1)*(7*x-1)*(8*x-1)*(9*x-1)). - Colin Barker, Oct 25 2012
E.g.f.: (exp(x) - 1)^9. - Ilya Gutkovskiy, Jun 19 2018

Extensions

More terms from Max Alekseyev, Nov 12 2009

A305625 Number of chiral pairs of rows of n colors with exactly 5 different colors.

Original entry on oeis.org

0, 0, 0, 0, 60, 900, 8400, 63000, 417000, 2551440, 14802900, 82763100, 450501660, 2404493700, 12645952200, 65771370000, 339164682000, 1737485315640, 8855354531100, 44952362878500, 227475739300260, 1148269299919500, 5785013208282000, 29100046926951000, 146201097996135000, 733811769167043840, 3680292427100043300, 18446421887430345900, 92412024657725026860, 462780012983867889300, 2316780309783100387800
Offset: 1

Views

Author

Robert A. Russell, Jun 06 2018

Keywords

Comments

If the row is achiral, i.e., the same as its reverse, we ignore it. If different from its reverse, we count it and its reverse as a chiral pair.

Examples

			For a(5) = 60, the chiral pairs are the 5! = 120 permutations of ABCDE, each paired with its reverse.
		

Crossrefs

Fifth column of A305622.
A056456(n) is number of achiral rows of n colors with exactly 5 different colors.

Programs

  • Mathematica
    k=5; Table[(k!/2) (StirlingS2[n,k] - StirlingS2[Ceiling[n/2],k]), {n, 1, 40}]
  • PARI
    a(n) = 60*(stirling(n, 5, 2) - stirling(ceil(n/2), 5, 2)); \\ Altug Alkan, Sep 26 2018

Formula

a(n) = (k!/2) * (S2(n,k) - S2(ceiling(n/2),k)), with k=5 colors used and where S2(n,k) is the Stirling subset number A008277.
a(n) = (A001118(n) - A056456(n)) / 2.
a(n) = A001118(n) - A056312(n) = A056312(n) - A056456(n).
G.f.: -(k!/2) * (x^(2k-1) + x^(2k)) / Product_{j=1..k} (1 - j*x^2) + (k!/2) * x^k / Product_{j=1..k} (1 - j*x) with k=5 colors used.

A371568 Array read by ascending antidiagonals: A(n, k) is the number of paths of length k in Z^n from the origin to points such that x1+x2+...+xn = k with x1,...,xn > 0.

Original entry on oeis.org

1, 0, 1, 0, 2, 1, 0, 0, 6, 1, 0, 0, 6, 14, 1, 0, 0, 0, 36, 30, 1, 0, 0, 0, 24, 150, 62, 1, 0, 0, 0, 0, 240, 540, 126, 1, 0, 0, 0, 0, 120, 1560, 1806, 254, 1, 0, 0, 0, 0, 1800, 8400, 5796, 510, 1
Offset: 1

Views

Author

Shel Kaphan, Mar 28 2024

Keywords

Comments

T(n, k) can also be seen as the number of ordered partitions of k items into n nonempty buckets.
T(n, n) = n!, which is readily seen because to go from the origin to a point in Z^n a distance n away, with at least one step taken in each dimension, the first step can be in any of n dimensions, the second step in any of n-1 dimensions, and so on.
This array is the image of Pascal's triangle A007318 under the Akiyama-Tanigawa transformation. See the Python program. - Peter Luschny, Apr 19 2024

Examples

			 n\k 1 2 3  4   5    6     7      8       9       10
  --------------------------------------------------
 1|  1 1 1  1   1    1     1      1       1        1
 2|  0 2 6 14  30   62   126    254     510     1022
 3|  0 0 6 36 150  540  1806   5796   18150    55980
 4|  0 0 0 24 240 1560  8400  40824  186480   818520
 5|  0 0 0  0 120 1800 16800 126000  834120  5103000
 6|  0 0 0  0   0  720 15120 191520 1905120 16435440
 7|  0 0 0  0   0    0  5040 141120 2328480 29635200
 8|  0 0 0  0   0    0     0  40320 1451520 30240000
 9|  0 0 0  0   0    0     0      0  362880 16329600
10|  0 0 0  0   0    0     0      0       0  3628800
		

Crossrefs

Cf. A000918 (n=2), A001117 (n=3), A000919 (n=4), A001118 (n=5), A000920 (n=6).
Cf. A135456 (n=7), A133068 (n=8), A133360 (n=9), A133132 (n=10).
See A019538 and A131689 for other versions.

Programs

  • Mathematica
    A[n_,k_] := Sum[(-1)^(n-i) * i^k * Binomial[n,i], {i,1,n}]
  • Python
    # The Akiyama-Tanigawa algorithm for the binomial generates the rows.
    # Adds row(0) = 0^k and column(0) = 0^n.
    from math import comb as binomial
    def ATBinomial(n, len):
        A = [0] * len
        R = [0] * len
        for k in range(len):
            R[k] = binomial(k, n)
            for j in range(k, 0, -1):
                R[j - 1] = j * (R[j] - R[j - 1])
            A[k] = R[0]
        return A
    for n in range(11): print([n], ATBinomial(n, 11))  # Peter Luschny, Apr 19 2024

Formula

A(n,k) = Sum_{i=1..n} (-1)^(n-i) * binomial(n,i) * i^k

A052785 a(n) = 5!*n*Stirling2(n-1, 5).

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 720, 12600, 134400, 1134000, 8341200, 56133000, 355291200, 2151864000, 12614281680, 72135063000, 404672486400, 2236228722000, 12209943566160, 66024457842600, 354214283304000, 1887999348060000, 10008933180578640, 52820388477271800, 277680637970208000
Offset: 0

Views

Author

encyclopedia(AT)pommard.inria.fr, Jan 25 2000

Keywords

Comments

Original name: a simple grammar.

Crossrefs

Programs

  • Maple
    spec := [S,{B=Set(Z,1 <= card),S=Prod(Z,B,B,B,B,B)},labeled]: seq(combstruct[count](spec,size=n), n=0..20);
  • PARI
    a(n)={if(n>=1, 5!*n*stirling(n-1, 5, 2), 0)} \\ Andrew Howroyd, Aug 08 2020

Formula

E.g.f.: x*exp(x)^5-5*x*exp(x)^4+10*exp(x)^3*x-10*exp(x)^2*x+5*x*exp(x)-x.
Recurrence: {a(1)=0, a(2)=0, a(4)=0, a(3)=0, a(5)=0, a(6)=720, ( - 14400 - 27000*n^2 - 32880*n - 120*n^5 - 1800*n^4 - 10200*n^3)*a(n) + (42196*n^2 + 19454*n^3 + 32880*n + 274*n^5 + 3836*n^4)*a(n + 1) + ( - 13500*n - 13275*n^3 - 24075*n^2 - 225*n^5 - 2925*n^4)*a(n + 2) + (85*n^5 + 3400*n + 1020*n^4 + 4165*n^3 + 6630*n^2)*a(n + 3) + ( - 915*n^2 - 450*n - 615*n^3 - 15*n^5 - 165*n^4)*a(n + 4) + (n^5 + 10*n^4 + 35*n^3 + 50*n^2 + 24*n)*a(n + 5)}.
From Andrew Howroyd, Aug 08 2020: (Start)
a(n) = n*A001118(n-1) for n > 1.
G.f.: 120*x^6*(2 - 5*x)*(3 - 30*x + 95*x^2 - 100*x^3 + 24*x^4)/((1 - x)*(1 - 2*x)*(1 - 3*x)*(1 - 4*x)*(1 - 5*x))^2.
E.g.f.: x*(exp(x) - 1)^5. (End)

Extensions

Name changed and terms a(21) and beyond from Andrew Howroyd, Aug 08 2020

A056270 Number of primitive (aperiodic) words of length n which contain exactly five different symbols.

Original entry on oeis.org

0, 0, 0, 0, 120, 1800, 16800, 126000, 834120, 5102880, 29607600, 165526200, 901020120, 4808987400, 25292030280, 131542740000, 678330198120, 3474970629480, 17710714165200, 89904725757000
Offset: 1

Views

Author

Keywords

References

  • M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia. [See A056391 for pdf file of Chap. 2]

Crossrefs

Formula

Sum mu(d)*A001118(n/d) where d|n.
Previous Showing 11-16 of 16 results.