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.

Showing 1-5 of 5 results.

A143965 Factorial eigentriangle: A119502 * (A051295 *0^(n-k)); 0 <= k <= n.

Original entry on oeis.org

1, 1, 1, 2, 1, 2, 6, 2, 2, 5, 24, 6, 4, 5, 15, 120, 24, 12, 10, 15, 54, 720, 120, 48, 30, 30, 54, 235, 5040, 720, 240, 120, 90, 108, 235, 1237, 40320, 5040, 1440, 600, 360, 324, 470, 1237, 7790
Offset: 0

Views

Author

Gary W. Adamson, Sep 06 2008

Keywords

Comments

Triangle read by rows, termwise product of (n-k)! (i.e factorial decrescendo,
A119502) and the INVERT transform of the factorials (A051295) prefaced by a 1:
(1, 1, 2, 5, 15, 54, 235, 1237, 7790, ...). A119502 = (1; 1,1; 2,1,1; 6,2,1,1; 24,6,2,1,1; ...).
The operation (A051295 * 0^(n-k)) with A051295 prefaced with a 1 = an infinite lower triangular matrix with (1, 1, 2, 5, 15, 54, 235, ...) in the main diagonal and the rest zeros.
Row sums = the INVERT transform of the factorials, A051295: (1, 2, 5, 15, 54, 235, 1237, ...).
Right border shifts A051295: (1, 1, 2, 5, 15, ...).
Sum of n-th row terms = rightmost term of next row; e.g. ( 6 + 2 + 2 + 5) = 15.
With offset 1 for n and k, T(n,k) counts permutations of [n] that contain a 132 pattern only as part of a 4132 pattern by position k of largest entry n. Example: T(5,3)=4 counts 34512, 34521, 43512, 43521. - David Callan, Nov 21 2011
From Gary W. Adamson, Jul 21 2016: (Start)
A production matrix M for the reversal of the triangle is follows: M =
1, 1, 0, 0, 0, 0, ...
1, 0, 2, 0, 0, 0, ...
1, 0, 0, 3, 0, 0, ...
1, 0, 0, 0, 4, 0, ...
1, 0, 0, 0, 0, 5, ...
... Take powers of M, extracting the top row, getting: (1), (1, 1), (2, 1, 2), (5, 2, 2, 6), ... (End)

Examples

			First few rows of the triangle:
     1;
     1,   1;
     2,   1,   2;
     6,   2,   2,   5;
    24,   6,   4,   5, 15;
   120,  24,  12,  10, 15,  54;
   720, 120,  48,  30, 30,  54, 235;
  5040, 720, 240, 120, 90, 108, 235, 1737;
  ...
Example: Row 3 = (6, 2, 2, 5) = termwise products of row 3 terms of triangle A119502 (6, 2, 1, 1) and the first four terms of (1, 1, 2, 5, ...) = (6*1, 2*1, 1*2, 1*5).
		

Crossrefs

Formula

Factorial eigentriangle: A119502 * (A051295 *0^(n-k)); 0 <= k <= n.
The operation uses A119502 prefaced with a 1 = (1, 1, 2, 5, 15, 54, 235, ...); i.e., the right border of the triangle.

A072597 Expansion of 1/(exp(-x) - x) as exponential generating function.

Original entry on oeis.org

1, 2, 7, 37, 261, 2301, 24343, 300455, 4238153, 67255273, 1185860331, 23000296155, 486655768525, 11155073325917, 275364320099807, 7282929854486431, 205462851526617489, 6158705454187353297, 195465061563672788947, 6548320737474275229347, 230922973019493881984021
Offset: 0

Views

Author

Michael Somos, Jun 23 2002

Keywords

Comments

Polynomials from A140749/A141412 are linked to Stirling1 (see A048594, A129841, A140749). See also P. Flajolet, X. Gourdon, B. Salvy in, available on Internet, RR-1857.pdf (preprint of unavailable Gazette des Mathematiciens 55, 1993, pp. 67-78; for graph 2 see also X. Gourdon RR-1852.pdf, pp. 64-65). What is the corresponding graph for A152650/A152656 = simplified A009998/A119502 linked, via A152818, to a(n), then Stirling2? - Paul Curtz, Dec 16 2008
Denominators in rational approximations of Lambert W(1). See Ramanujan, Notebooks, volume 2, page 22: "2. If e^{-x} = x, shew that the convergents to x are 1/2, 4/7, 21/37, 148/261, &c." Numerators in A006153. - Michael Somos, Jan 21 2019
Call an element g in a semigroup a group element if g^j = g for some j > 1. Then a(n) is the number of group elements in the semigroup of partial transformations of an n-set. Hence a(n) = Sum_{k=0..n} A154372(n,k)*k!. - Geoffrey Critzer, Nov 27 2021

Examples

			G.f. = 1 + 2*x + 7*x^2 + 37*x^3 + 261*x^4 + 2301*x^5 + 24343*x^6 + ...
		

References

  • O. Ganyushkin and V Mazorchuk, Classical Finite Transformation Semigroups, Springer, 2009, page 70.
  • S. Ramanujan, Notebooks, Tata Institute of Fundamental Research, Bombay 1957 Vol. 2, see page 22.

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[1/(Exp[-x]-x), {x, 0, 20}], x]* Range[0, 20]! (* Vaclav Kotesovec, Jun 26 2013 *)
    a[ n_] := If[ n < 0, 0, n! SeriesCoefficient[ 1 / (Exp[-x] - x), {x, 0, n}]]; (* Michael Somos, Jan 21 2019 *)
    a[ n_] := If[ n < 0, 0, n! Sum[ (n - k + 1)^k / k!, {k, 0, n}]]; (* Michael Somos, Jan 21 2019 *)
  • PARI
    {a(n) = if( n<0, 0, n! * polcoeff( 1 / (exp(-x + x * O(x^n)) - x), n))};
    
  • PARI
    {a(n) = if( n<0, 0, n! * sum(k=0, n, (n-k+1)^k / k!))}; /* Michael Somos, Jan 21 2019 */

Formula

E.g.f.: 1 / (exp(-x) - x).
a(n) = n!*Sum_{k=0..n} (n-k+1)^k/k!. - Vladeta Jovovic, Aug 31 2003
a(n) = Sum_{k=0..n} (-1)^(n-k)*Stirling2(n, k)*A052820(k). - Vladeta Jovovic, Apr 12 2004
Recurrence: a(n+1) = 1 + Sum_{j=1..n} binomial(n, j)*a(j)*j. - Jon Perry, Apr 25 2005
E.g.f.: 1/(Q(0) - x) where Q(k) = 1 - x/(2*k+1 - x*(2*k+1)/(x - (2*k+2)/Q(k+1) )); (continued fraction ). - Sergei N. Gladkovskii, Apr 04 2013
a(n) ~ n!/((1+c)*c^(n+1)), where c = A030178 = LambertW(1) = 0.5671432904... - Vaclav Kotesovec, Jun 26 2013
O.g.f.: Sum_{k>=0} k!*x^k/(1 - (k + 1)*x)^(k+1). - Ilya Gutkovskiy, Oct 09 2018
a(n) = A006153(n+1)/(n+1). - Seiichi Manyama, Nov 05 2024

A152818 Array read by antidiagonals: A(n,k) = (k+1)^n*(n+k)!/n!.

Original entry on oeis.org

1, 1, 1, 1, 4, 2, 1, 12, 18, 6, 1, 32, 108, 96, 24, 1, 80, 540, 960, 600, 120, 1, 192, 2430, 7680, 9000, 4320, 720, 1, 448, 10206, 53760, 105000, 90720, 35280, 5040, 1, 1024, 40824, 344064, 1050000, 1451520, 987840, 322560, 40320
Offset: 0

Views

Author

Paul Curtz, Dec 13 2008

Keywords

Comments

A009998/A119502 gives triangle of unreduced coefficients of polynomials defined by A152650/A152656. a(n) gives numerators with denominators n! for each row.
Row 0 is A000142. Row 1 is formed from positive members of A001563. Row 2 is A055533. Column 0 is A000012. Column 1 is formed from positive members of A001787. Column 2 is A006043. Column 3 is A006044. - Omar E. Pol, Jan 06 2009

Examples

			From _Omar E. Pol_, Jan 06 2009: (Start)
Array begins:
  1,    1,      2,        6,         24,          120, ...
  1,    4,     18,       96,        600,         4320, ...
  1,   12,    108,      960,       9000,        90720, ...
  1,   32,    540,     7680,     105000,      1451520, ...
  1,   80,   2430,    53760,    1050000,     19595520, ...
  1,  192,  10206,   344064,    9450000,    235146240, ...
  1,  448,  40824,  2064384,   78750000,   2586608640, ...
  1, 1024, 157464, 11796480,  618750000,  26605117440, ...
  1, 2304, 590490, 64880640, 4640625000, 259399895040, ... (End)
Antidiagonal triangle:
  1;
  1,   1;
  1,   4,     2;
  1,  12,    18,     6;
  1,  32,   108,    96,     24;
  1,  80,   540,   960,    600,   120;
  1, 192,  2430,  7680,   9000,  4320,   720;
  1, 448, 10206, 53760, 105000, 90720, 35280, 5040;
		

Crossrefs

Programs

  • Magma
    A152818:= func< n,k | (k+1)^(n-k)*Factorial(k)*Binomial(n,k) >;
    [A152818(n,k): k in [0..n], n in [0..12]]; // G. C. Greubel, Apr 10 2023
  • Mathematica
    len= 45; m= 1 + Ceiling[Sqrt[len]]; Sort[Flatten[#, 1] &[MapIndexed[ {(2 +#2[[1]]^2 +(#2[[2]] -1)*#2[[2]] +#2[[1]]*(2*#2[[2]] -3))/ 2, #1}&, Table[(k+1)^n*(n+k)!/n!, {n,0,m}, {k,0,m}], {2}]]][[All, 2]][[1 ;; len]] (* From Jean-François Alcover, May 27 2011 *)
    T[n_, k_]:= (k+1)^(n-k)*k!*Binomial[n, k];
    Table[T[n,k], {n,0,15}, {k,0,n}]//Flatten (* G. C. Greubel, Apr 10 2023 *)
  • PARI
    A(n,k) = (k+1)^n*(n+k)!/n! \\ Charles R Greathouse IV, Sep 10 2016
    
  • Sage
    def A152818_row(n):
        R. = ZZ[]
        P = add((n-k+1)^k*x^(n-k+1)*factorial(n)/factorial(k) for k in (0..n))
        return P.coefficients()
    for n in (0..12): print(A152818_row(n))  # Peter Luschny, May 03 2013
    

Formula

E.g.f. for array as a triangle: exp(x)/(1-t*x*exp(x)) = 1+(1+t)*x+(1+4*t+2*t^2)*x^2/2! + (1+12*t+18*t^2+6*t^3)*x^3/3! + .... E.g.f. is int {z = 0..inf} exp(-z)*F(x,t*z), (x and t chosen sufficiently small for the integral to converge), where F(x,t) = exp(x*(1+t*exp(x))) is the e.g.f. for A154372. - Peter Bala, Oct 09 2011
From Peter Bala, Oct 09 2011: (Start)
From the e.g.f., the row polynomials R(n,t) satisfy the recursion R(n,t) = 1 + t*sum {k = 0..n-1} n!/(k!*(n-k-1)!)*R(n-k-1,t). The polynomials 1/n!*R(n,x) are the polynomials P(n,x) of A152650.
Sum_{k=0..n} T(n, k) = A072597(n) (antidiagonal sums). (End)
From G. C. Greubel, Apr 10 2023: (Start)
T(n, k) = (k+1)^(n-k) * k! * binomial(n, k) (antidiagonal triangle).
Sum_{k=0..n} (-1)^k*T(n, k) = A089148(n). (End)

Extensions

Better definition, extended and edited by Omar E. Pol and N. J. A. Sloane, Jan 05 2009

A374162 a(n) is the number of permutations of size n ending with n whose n left-to-right maxima are consecutive and nonadjacent.

Original entry on oeis.org

1, 0, 1, 2, 8, 36, 198, 1272, 9384, 78240, 728040, 7482960, 84224160, 1030569120, 13623366960, 193515477120, 2939860748160, 47568519613440, 816772822750080, 14833749363552000, 284114908317542400, 5723753780712844800, 120995656719515424000, 2678008828724659584000
Offset: 1

Views

Author

Stefano Spezia, Jun 30 2024

Keywords

Crossrefs

Programs

  • Mathematica
    a[1]=1; a[n_]:=Sum[(n-k)!Binomial[n-k-1,k-2],{k,2,Ceiling[n/2]}]; Array[a,24]

Formula

a(1) = 1 and a(n) = Sum_{k=2..ceiling(n/2)} (n-k)!*binomial(n-k-1, k-2) for n > 1.

A370418 Triangle read by rows. T(n, k) = (n - k)! * (n + k)!.

Original entry on oeis.org

1, 1, 2, 4, 6, 24, 36, 48, 120, 720, 576, 720, 1440, 5040, 40320, 14400, 17280, 30240, 80640, 362880, 3628800, 518400, 604800, 967680, 2177280, 7257600, 39916800, 479001600, 25401600, 29030400, 43545600, 87091200, 239500800, 958003200, 6227020800, 87178291200
Offset: 0

Views

Author

Peter Luschny, Feb 27 2024

Keywords

Examples

			Triangle starts:
[0]      1;
[1]      1,      2;
[2]      4,      6,     24;
[3]     36,     48,    120,     720;
[4]    576,    720,   1440,    5040,   40320;
[5]  14400,  17280,  30240,   80640,  362880,  3628800;
[6] 518400, 604800, 967680, 2177280, 7257600, 39916800, 479001600;
		

Crossrefs

Cf. A010050 (main diagonal), A009445 (subdiagonal), A001044 (column 0), A175430 (column 1), A024420 (bisection is alternating sum).

Programs

  • Maple
    T := (n, k) -> (n - k)! * (n + k)!:
    seq(seq(T(n, k), k = 0..n), n = 0..7);
  • Mathematica
    Table[(n - k)!*(n + k)!, {n, 0, 7}, {k, 0, n}] // Flatten (* Michael De Vlieger, Mar 05 2024 *)

Formula

Sum_{k=0..n} (-1)^k*T(n, k) = n!^2 / 2 + (-1)^n * (2*n + 2)! / (2*n + 2)^2.
Showing 1-5 of 5 results.