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 42 results. Next

A001755 Lah numbers: a(n) = n! * binomial(n-1, 3)/4!.

Original entry on oeis.org

1, 20, 300, 4200, 58800, 846720, 12700800, 199584000, 3293136000, 57081024000, 1038874636800, 19833061248000, 396661224960000, 8299373322240000, 181400588328960000, 4135933413900288000, 98228418580131840000, 2426819753156198400000, 62288373664342425600000
Offset: 4

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Author

Keywords

References

  • Louis Comtet, Advanced Combinatorics, Reidel, 1974, p. 156.
  • John Riordan, An Introduction to Combinatorial Analysis, Wiley, 1958, p. 44.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Column 4 of A008297.
Column m=4 of unsigned triangle A111596.
Cf. A053495.

Programs

  • Magma
    [Factorial(n-1)*Binomial(n, 4)/6: n in [4..30]]; // G. C. Greubel, May 10 2021
  • Maple
    A001755 := n-> n!*binomial(n-1,3)/4!;
  • Mathematica
    Table[n!Binomial[n-1, 3]/4!, {n, 4, 25}] (* T. D. Noe, Aug 10 2012 *)
  • Sage
    [binomial(n,4)*factorial (n-1)/6 for n in range(4, 21)] # Zerinvary Lajos, Jul 07 2009
    

Formula

E.g.f.: ((x/(1-x))^4)/4!.
If we define f(n,i,x) = Sum_{k=i..n} (Sum_{j=i..k} (binomial(k,j) * Stirling1(n,k) * Stirling2(j,i) * x^(k-j) ) ) then a(n) = (-1)^n*f(n,4,-4), (n>=4). - Milan Janjic, Mar 01 2009
D-finite with recurrence (-n+4)*a(n) +n*(n-1)*a(n-1)=0. - R. J. Mathar, Jan 06 2021
From Amiram Eldar, May 02 2022: (Start)
Sum_{n>=4} 1/a(n) = 12*(Ei(1) - gamma + 2*e) - 80, where Ei(1) = A091725, gamma = A001620, and e = A001113.
Sum_{n>=4} (-1)^n/a(n) = 156*(gamma - Ei(-1)) - 96/e - 88, where Ei(-1) = -A099285. (End)

Extensions

More terms from Barbara Haas Margolius (margolius(AT)math.csuohio.edu), Feb 12 2001

A001777 Lah numbers: a(n) = n! * binomial(n-1, 4)/5!.

Original entry on oeis.org

1, 30, 630, 11760, 211680, 3810240, 69854400, 1317254400, 25686460800, 519437318400, 10908183686400, 237996734976000, 5394592659456000, 126980411830272000, 3101950060425216000, 78582734864105472000, 2062796790182768640000, 56059536297908183040000
Offset: 5

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Author

Keywords

References

  • Louis Comtet, Advanced Combinatorics, Reidel, 1974, p. 156.
  • John Riordan, An Introduction to Combinatorial Analysis, Wiley, 1958, p. 44.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Column 5 of A008297. Cf. A053495.
Column m=5 of unsigned triangle A111596.

Programs

  • Maple
    A001777 := n-> n!*binomial(n-1,4)/5!;
  • Mathematica
    Table[n! Binomial[n - 1, 4]/5!, {n, 5, 20}] (* T. D. Noe, Aug 10 2012 *)
  • Sage
    [binomial(n,5)*factorial (n-1)/factorial (4) for n in range(5, 21)] # Zerinvary Lajos, Jul 07 2009

Formula

E.g.f.: ((x/(1-x))^5)/5!.
If we define f(n,i,x) = sum(sum(binomial(k,j)*Stirling1(n,k)*Stirling2(j,i)*x^(k-j),j=i..k),k=i..n) then a(n+1)=(-1)^n*f(n,4,-6), (n>=4). - Milan Janjic, Mar 01 2009
From Amiram Eldar, May 02 2022: (Start)
Sum_{n>=5} 1/a(n) = 20*(Ei(1) - gamma) - 200*e + 1555/3, where Ei(1) = A091725, gamma = A001620, and e = A001113.
Sum_{n>=5} (-1)^(n+1)/a(n) = 1460*(gamma - Ei(-1)) - 880/e - 2515/3, where Ei(-1) = -A099285. (End)

Extensions

More terms from Barbara Haas Margolius (margolius(AT)math.csuohio.edu)

A187543 Binomial convolutions of the central Lah numbers (A187535).

Original entry on oeis.org

1, 4, 80, 2832, 144576, 9660480, 798468480, 78670609920, 9002061573120, 1173384611804160, 171641216823552000, 27843893955582566400, 4961007038613633638400, 963075987422089673932800, 202333751987206944654950400
Offset: 0

Views

Author

Emanuele Munarini, Mar 11 2011

Keywords

Crossrefs

Programs

  • Maple
    a := n -> if n=0 then 1 else binomial(2*n-1,n-1)*(2*n)!/n! fi;
    seq(add(binomial(n,k)*a(k)*a(n-k), k=0..n),n=0..12);
  • Mathematica
    a[n_] := If[n == 0, 1, Binomial[2n - 1, n - 1](2n)!/n!]
    Table[Sum[Binomial[n, k]a[k]a[n - k], {k, 0, n}], {n, 0, 20}]
    CoefficientList[Series[(1/2 + EllipticK[16*x]/Pi)^2, {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Oct 06 2019 *)
  • Maxima
    a(n):= if n=0 then 1 else binomial(2*n-1,n-1)*(2*n)!/n!;
    makelist(sum(binomial(n,k)*a(k)*a(n-k),k,0,n),n,0,12);

Formula

a(n) = sum(binomial(n,k)*L(k)*L(n-k),k=0..n), where L(n) is a central Lah number.
E.g.f.: (1/2 + 1/Pi*K(16x))^2, where K(z) is the elliptic integral of the first kind (defined as in Mathematica).
Recurrence: (n-1)*n^2*(4*n^2-15*n+13)*a(n) = 4*(n-1)*(48*n^5-292*n^4+672*n^3-747*n^2+399*n-76)*a(n-1) - 32*(96*n^7-1000*n^6+4408*n^5-10628*n^4+15034*n^3-12312*n^2+5265*n-854)*a(n-2) + 1024*(2*n-5)^2*(4*n^2-7*n+2)*(n-2)^4*a(n-3). - Vaclav Kotesovec, Aug 10 2013
a(n) ~ n! * log(n) * 2^(4*n-1) / (Pi^2 * n) * (1 + (gamma + Pi + 4*log(2)) / log(n)), where gamma is the Euler-Mascheroni constant A001620. - Vaclav Kotesovec, Oct 06 2019

A187544 Stirling transform (of the second kind) of the central Lah numbers (A187535).

Original entry on oeis.org

1, 2, 38, 1310, 66254, 4428782, 368444078, 36691056110, 4256199137774, 563672814445742, 83921091641375918, 13875375391723852910, 2522552600160248918894, 500141581330626431059502, 107400097037199576065830958
Offset: 0

Views

Author

Emanuele Munarini, Mar 11 2011

Keywords

Crossrefs

Programs

  • Maple
    a := n -> if n=0 then 1 else binomial(2*n-1,n-1)*(2*n)!/n! fi;
    seq(sum(combinat[stirling2](n,k)*a(k), k=0..n),n=0..12);
  • Mathematica
    a[n_] := If[n == 0, 1, Binomial[2n - 1, n - 1](2n)!/n!]
    Table[Sum[StirlingS2[n, k]a[k], {k, 0, n}], {n, 0, 20}]
    CoefficientList[Series[1/2 + EllipticK[16*(E^x - 1)]/Pi, {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Oct 06 2019 *)
  • Maxima
    a(n):= if n=0 then 1 else binomial(2*n-1,n-1)*(2*n)!/n!;
    makelist(sum(stirling2(n,k)*a(k),k,0,n),n,0,12);

Formula

a(n) = sum(S(n,k)*L(k),k=0..n), where S(n,k) are the Stirling numbers of the second kind and L(n) are the central Lah numbers.
E.g.f.: 1/2 + 1/Pi*K(16(exp(x)-1)) where K(z) is the elliptic integral of the first kind (defined as in Mathematica).
a(n) ~ n! / (2*Pi*n * (log(17/16))^n). - Vaclav Kotesovec, Oct 06 2019

A187545 Stirling transform (of the first kind) of the central Lah numbers (A187535).

Original entry on oeis.org

1, 2, 38, 1312, 66408, 4442088, 369791064, 36848702784, 4277191653888, 566809715422464, 84441103242634176, 13970100487593468480, 2541362625439551554880, 504185908064687887996800, 108336183242510523080868480
Offset: 0

Views

Author

Emanuele Munarini, Mar 11 2011

Keywords

Crossrefs

Programs

  • Maple
    lahc := n -> if n=0 then 1 else binomial(2*n-1,n-1)*(2*n)!/n! fi;
    seq(add(abs(combinat[stirling1](n,k))*lahc(k), k=0..n), n=0..20);
  • Mathematica
    lahc[n_] := If[n == 0, 1, Binomial[2n - 1, n - 1](2n)!/n!]
    Table[Sum[Abs[StirlingS1[n, k]]*lahc[k], {k, 0, n}], {n, 0, 20}]
  • Maxima
    lahc(n):= if n=0 then 1 else binomial(2*n-1,n-1)*(2*n)!/n!;
    makelist(sum(abs(stirling1(n,k))*lahc(k),k,0,n),n,0,12);

Formula

a(n) = sum(s(n,k)*L(k), k=0..n), where s(n,k) are the (signless) Stirling numbers of the first kind and L(n) are the central Lah numbers.
E.g.f.: 1/2 + 1/Pi*K(-16*log(1-x)), where K(z) is the elliptic integral of the first kind (defined as in Mathematica).
a(n) ~ n! / (2*Pi*n * (1 - exp(-1/16))^n). - Vaclav Kotesovec, Apr 10 2018

A187546 Stirling transform (of the first kind, with signs) of the central Lah numbers (A187535).

Original entry on oeis.org

1, 2, 34, 1096, 51984, 3262488, 254943384, 23853046656, 2600024557248, 323588157732096, 45276442446814656, 7035574740347812800, 1202158966644148296000, 224022356544364922931840, 45215509996613004825121920
Offset: 0

Views

Author

Emanuele Munarini, Mar 11 2011

Keywords

Crossrefs

Programs

  • Maple
    lahc := n -> if n=0 then 1 else binomial(2*n-1,n-1)*(2*n)!/n! fi;
    seq(add(combinat[stirling1](n,k)*lahc(k), k=0..n), n=0..20);
  • Mathematica
    lahc[n_] := If[n == 0, 1, Binomial[2n - 1, n - 1](2n)!/n!]
    Table[Sum[StirlingS1[n, k]*lahc[k], {k, 0, n}], {n, 0, 20}]
  • Maxima
    lahc(n):= if n=0 then 1 else binomial(2*n-1,n-1)*(2*n)!/n!;
    makelist(sum(stirling1(n,k)*lahc(k),k,0,n),n,0,12);

Formula

a(n) = sum((-1)^(n-k)*s(n,k)*L(k), k=0..n), where s(n,k) are the (signless) Stirling numbers of the first kind and L(n) are the central Lah numbers.
E.g.f.: 1/2 + 1/Pi*K(16*log(1+x)), where K(z) is the elliptic integral of the first kind (defined as in Mathematica).
a(n) ~ n! / (2*Pi*n * (exp(1/16) - 1)^n). - Vaclav Kotesovec, Apr 10 2018

A187547 L(n)H(n+1), product of the central Lah number L(n) and the harmonic number H(n).

Original entry on oeis.org

1, 3, 66, 2500, 134260, 9335088, 796938912, 80671795776, 9446603680800, 1256254443100800, 187033518310129920, 30821040496874234880, 5569495264653352381440, 1095113648992295923200000, 232773183612995427763200000, 53186532693832607435089920000
Offset: 0

Views

Author

Emanuele Munarini, Mar 11 2011

Keywords

Crossrefs

Programs

  • Maple
    a := n -> if n=0 then 1 else binomial(2*n-1,n-1)*(2*n)!/n! fi;
    seq(a(n)*sum(1/k,k=1..n+1),n=0..12);
  • Mathematica
    a[n_] := If[n == 0, 1, Binomial[2n - 1, n - 1](2n)!/n!]
    Table[a[n]HarmonicNumber[n + 1], {n, 0, 20}]
  • Maxima
    a(n):= if n=0 then 1 else binomial(2*n-1,n-1)*(2*n)!/n!;
    makelist(a(n)*sum(1/k,k,1,n+1),n,0,12);

Formula

Recurrence:
(n+3)(n+2)(n+1)a(n+2)-4(2n+3)^2(2n+5)(n+1)a(n+1)+16(2n+3)^2(2n+1)^2(n+2)a(n)-144delta(n,0)=0.

A235706 (I + A132440)^3: Coefficients for normalized generalized Laguerre polynomials n!*Lag(n, 3-n, -x).

Original entry on oeis.org

1, 3, 1, 6, 6, 1, 6, 18, 9, 1, 0, 24, 36, 12, 1, 0, 0, 60, 60, 15, 1, 0, 0, 0, 120, 90, 18, 1, 0, 0, 0, 0, 210, 126, 21, 1, 0, 0, 0, 0, 0, 336, 168, 24, 1, 0, 0, 0, 0, 0, 0, 504, 216, 27, 1, 0, 0, 0, 0, 0, 0, 0, 720, 270, 30, 1
Offset: 0

Views

Author

Tom Copeland, Apr 20 2014

Keywords

Comments

The associated Laguerre polynomials n!*Lag(n,3-n,-x) are related to the rook polynomials of a rectangular 3 X n chessboard by R(3,n,x) = n!*x^n*Lag(n,3-n,-1/x), which are also the matching polynomials, or generating function of the number of k-edge matchings, of the complete bipartite graph K(m,n), or biclique (cf. Wikipedia for details).
The formulas here and below can be naturally extended with 3 replaced by any positive integer m. For m = 1 and 2, see unsigned A132013 and A132014. The formulas there can be extrapolated to apply to this matrix.

Examples

			Triangle begins:
  1;
  3,  1;
  6,  6,  1;
  6, 18,  9,  1;
  0, 24, 36, 12,  1;
  0,  0, 60, 60, 15, 1;
  ...
		

Crossrefs

Cf. A007318, A008306 for a generalization, A132013, A132014, A132440, A238363, A238385.
....................................
With 0th row: 1
n-th row: n!*Lag(n,3-n,-x)
....................................
1st: 1!*Lag(1,2,-x) = A062139(1,k,-x)
2nd: 2!*Lag(2,1,-x) = A105278(2,k,x)
3rd: 3!*Lag(3,0,-x) = A021009(3,k,-x)
4th: 4!*Lag(4,-1,-x) = A111596(4,k,-x)
5th: 5!*Lag(5,-2,-x) = cf. x^2*A062139(3,k,x)
6th: 6!*Lag(6,-3,-x) = cf. x^3*A062137(3,k,-x)
....................................
n-th row: x^(n-3)*3!*Lag(3,n-3,-x)
....................................
1st: x^(-2)*3!Lag(3,-2,-x) = cf. x^(-2)*[x^2*A062139(1,k,x)]
2nd: x^(-1)*3!Lag(3,-1,-x) = x^(-1)*A111596(3,k,-x)
3rd: x^0*3!Lag(3,0,-x) = x^0*A021009(3,k,-x)
4th: x^1*3!Lag(3,1,-x) = x^1*A105278(3,k,x)
5th: x^2*3!Lag(3,2,-x) = x^2*A062139(3,k,-x)
6th: x^3*3!Lag(3,3,-x) = x^3*A062137(3,k,-x)

Programs

  • Magma
    /* As triangle */ [[Binomial(3, n-k)*Factorial(n)/Factorial(k): k in [0..n]]: n in [0.. 15]]; // Vincenzo Librandi, Jul 28 2017
  • Mathematica
    Table[Binomial[3, n - k] n! / k!, {n, 0, 9}, {k, 0, n}]//Flatten (* Vincenzo Librandi, Jul 28 2017 *)
  • PARI
    T(n,k) = binomial(3,n-k)*n!/k!
    tabl(nn) = for (n=0, nn, for (k=0, n, print1(T(n, k), ", ")); print); \\ Michel Marcus, Jul 28 2017
    
  • PARI
    row(n) = Vecrev(n!*pollaguerre(n, 3-n, -x)); \\ Michel Marcus, Feb 06 2021
    

Formula

T(n,k) = binomial(3,n-k)*n!/k! = binomial(n,k)*3!/(3-n+k)!.
E.g.f.: exp(y*x)(1+y)^3, so this is an Appell sequence of polynomials with lowering operator L= D= d/dx and raising operator R = x + 3/(1+D).
E.g.f. of inverse matrix is exp(x*y)/(1+y)^3.
Multiply the n-th diagonal of the Pascal matrix A007318 by d(0)=1, d(1)=3, d(2)=6, d(3)=6, and d(n)=0 for n>3 to obtain T.
Row polynomials: n!*Lag(n,3-n,-x) = x^(n-3)*3!*Lag(3,n-3,-x) =
(3!/(3-n)!)*K(-n,3-n+1,-x) where K is Kummer's confluent hypergeometric function (as a limit of n+c as c tends to zero).
T = (I + A132440)^3 = exp[3*(A238385-I)]. I = identity matrix.
Operationally, n!Lag(n,3-n,-:xD:) = x^(n-3)*:Dx:^n*x^(3-n) = x^(-3)*:xD:^n*x^3 = n!*binomial(xD+3,n) = n!*binomial(3,n)*K(-n,3-n+1,-:xD:) where :AB:^n = A^n*B^n for any two operators.
n-th row polynomial: n!*Sum_{k = 0..n} (-1)^(n-k)*binomial(n,k)*Lag(k,3,-x). - Peter Bala, Jul 25 2021

A351641 Triangle read by rows: T(n,k) is the number of length n word structures with all distinct runs using exactly k different symbols.

Original entry on oeis.org

1, 0, 1, 0, 1, 1, 0, 1, 2, 1, 0, 1, 5, 3, 1, 0, 1, 8, 12, 4, 1, 0, 1, 17, 28, 22, 5, 1, 0, 1, 26, 81, 68, 35, 6, 1, 0, 1, 45, 177, 251, 135, 51, 7, 1, 0, 1, 76, 410, 704, 610, 236, 70, 8, 1, 0, 1, 121, 906, 2068, 2086, 1266, 378, 92, 9, 1
Offset: 0

Views

Author

Andrew Howroyd, Feb 15 2022

Keywords

Comments

Permuting the symbols will not change the structure.
Equivalently, T(n,k) is the number of restricted growth strings [s(0), s(1), ..., s(n-1)] where s(0)=0 and s(i) <= 1 + max(prefix) for i >= 1, the maximum value is k and all runs are distinct.

Examples

			Triangle begins:
  1;
  0, 1;
  0, 1,  1;
  0, 1,  2,   1;
  0, 1,  5,   3,   1;
  0, 1,  8,  12,   4,   1;
  0, 1, 17,  28,  22,   5,  1;
  0, 1, 26,  81,  68,  35,  6, 1;
  0, 1, 45, 177, 251, 135, 51, 7, 1;
  ...
The T(4,1) = 1 word is 1111.
The T(4,2) = 5 words are 1112, 1121, 1122, 1211, 1222.
The T(4,3) = 3 words are 1123, 1223, 1233.
The T(4,4) = 1 word is 1234.
		

Crossrefs

Row sums are A351642.
Partial row sums include A000007, A000012, A351018, A351644.
Column k=3 is A351643.

Programs

  • PARI
    \\ here LahI is A111596 as row polynomials.
    LahI(n, y)={sum(k=1, n, y^k*(-1)^(n-k)*(n!/k!)*binomial(n-1, k-1))}
    S(n)={my(p=prod(k=1, n, 1 + y*x^k + O(x*x^n))); 1 + sum(i=1, (sqrtint(8*n+1)-1)\2, polcoef(p, i, y)*LahI(i, y))}
    R(q)={[subst(serlaplace(p), y, 1) | p<-Vec(q)]}
    T(n)={my(q=S(n), v=concat([1], sum(k=1, n, R(q^k-1)*sum(r=k, n, y^r*binomial(r, k)*(-1)^(r-k)/r!) ))); [Vecrev(p) | p<-v]}
    { my(A=T(10)); for(n=1, #A, print(A[n])) }

Formula

T(n,k) = A351640(n,k)/k!.

A001778 Lah numbers: a(n) = n!*binomial(n-1,5)/6!.

Original entry on oeis.org

1, 42, 1176, 28224, 635040, 13970880, 307359360, 6849722880, 155831195520, 3636061228800, 87265469491200, 2157837063782400, 55024845126451200, 1447576694865100800, 39291367432052736000, 1100158288097476608000, 31767070568814637056000
Offset: 6

Views

Author

Keywords

References

  • Louis Comtet, Advanced Combinatorics, Reidel, 1974, p. 156.
  • John Riordan, An Introduction to Combinatorial Analysis, Wiley, 1958, p. 44.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Column 6 of A008297.
Column m=6 of unsigned triangle A111596.

Programs

  • Magma
    [Factorial(n-6)*Binomial(n,6)*Binomial(n-1,5): n in [6..30]]; // G. C. Greubel, May 10 2021
  • Maple
    A001778 := proc(n)
        n!*binomial(n-1,5)/6! ;
    end proc:
    seq(A001778(n),n=6..30) ; # R. J. Mathar, Jan 06 2021
  • Mathematica
    With[{c=6!},Table[n!Binomial[n-1,5]/c,{n,6,24}]] (* Harvey P. Dale, May 25 2011 *)
  • Sage
    [binomial(n,6)*factorial(n-1)/factorial(5) for n in range(6, 22)] # Zerinvary Lajos, Jul 07 2009
    

Formula

E.g.f.: ((x/(1-x))^6)/6!.
If we define f(n,i,x) = Sum_{k=i..n} (Sum_{j=i..k} (binomial(k,j)*Stirling1(n,k) *Stirling2(j,i)*x^(k-j) ) ) then a(n) = (-1)^n*f(n,6,-6), (n>=6). - Milan Janjic, Mar 01 2009
D-finite with recurrence (-n+6)*a(n) +n*(n-1)*a(n-1)=0. - R. J. Mathar, Jan 06 2021
From Amiram Eldar, May 02 2022: (Start)
Sum_{n>=6} 1/a(n) = 570*(gamma - Ei(1)) + 1380*e - 2999, where gamma = A001620, Ei(1) = A091725 and e = A001113.
Sum_{n>=6} (-1)^n/a(n) = 15030*(gamma - Ei(-1)) - 9000/e - 8661, where Ei(-1) = -A099285. (End)

Extensions

More terms from Christian G. Bower, Dec 18 2001
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