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.

A136394 Triangle read by rows: T(n,k) is the number of permutations of an n-set having k cycles of size > 1 (0<=k<=floor(n/2)).

Original entry on oeis.org

1, 1, 1, 1, 1, 5, 1, 20, 3, 1, 84, 35, 1, 409, 295, 15, 1, 2365, 2359, 315, 1, 16064, 19670, 4480, 105, 1, 125664, 177078, 56672, 3465, 1, 1112073, 1738326, 703430, 74025, 945, 1, 10976173, 18607446, 8941790, 1346345, 45045, 1, 119481284, 216400569, 118685336
Offset: 0

Views

Author

Vladeta Jovovic, May 03 2008

Keywords

Examples

			Triangle (n,k) begins:
  1;
  1;
  1,    1;
  1,    5;
  1,   20,    3;
  1,   84,   35;
  1,  409,  295,  15;
  1, 2365, 2359, 315;
  ...
		

Crossrefs

Programs

  • Maple
    egf:= proc(k::nonnegint) option remember; x-> exp(x)* ((-x-ln(1-x))^k)/k! end; T:= (n,k)-> coeff(series(egf(k)(x), x=0, n+1), x, n) *n!; seq(seq(T(n,k), k=0..n/2), n=0..30); # Alois P. Heinz, Aug 14 2008
    # second Maple program:
    b:= proc(n) option remember; expand(`if`(n=0, 1, add(b(n-i)*
          `if`(i>1, x, 1)*binomial(n-1, i-1)*(i-1)!, i=1..n)))
        end:
    T:= n-> (p-> seq(coeff(p, x, i), i=0..degree(p)))(b(n)):
    seq(T(n), n=0..15);  # Alois P. Heinz, Sep 25 2016
    # third Maple program:
    T:= proc(n, k) option remember; `if`(k<0 or k>2*n, 0,
          `if`(n=0, 1, add(T(n-i, k-`if`(i>1, 1, 0))*
           mul(n-j, j=1..i-1), i=1..n)))
        end:
    seq(seq(T(n,k), k=0..n/2), n=0..15);  # Alois P. Heinz, Jul 16 2017
  • Mathematica
    max = 12; egf = Exp[x*(1-y)]/(1-x)^y; s = Series[egf, {x, 0, max}, {y, 0, max}] // Normal; t[n_, k_] := SeriesCoefficient[s, {x, 0, n}, {y, 0, k}]*n!; t[0, 0] = t[1, 0] = 1; Table[t[n, k], {n, 0, max}, {k, 0, n/2}] // Flatten (* Jean-François Alcover, Jan 28 2014 *)

Formula

E.g.f.: exp(x*(1-y))/(1-x)^y. Binomial transform of triangle A008306. exp(x)*((-x-log(1-x))^k)/k! is e.g.f. of k-th column.
From Alois P. Heinz, Jul 13 2017: (Start)
T(2n,n) = A001147(n).
T(2n+1,n) = A051577(n) = (2*n+3)!!/3 = A001147(n+2)/3. (End)
From Alois P. Heinz, Aug 17 2023: (Start)
Sum_{k=0..floor(n/2)} k * T(n,k) = A001705(n-1) for n>=1.
Sum_{k=0..floor(n/2)} (-1)^k * T(n,k) = A159964(n-1) for n>=1. (End)

A137346 Coefficients of a special case of Poisson-Charlier polynomials. Triangle read by rows, T(n, k) for 0 <= k <= n.

Original entry on oeis.org

1, -2, 1, 4, -5, 1, -8, 20, -9, 1, 16, -78, 59, -14, 1, -32, 324, -360, 135, -20, 1, 64, -1520, 2254, -1165, 265, -27, 1, -128, 8336, -15232, 9954, -3045, 469, -35, 1, 256, -53872, 113868, -88508, 33649, -6888, 770, -44, 1, -512, 405600, -948840, 839684, -376278, 95025, -14028, 1194, -54
Offset: 0

Views

Author

Roger L. Bagula, Apr 08 2008

Keywords

Examples

			{1},
{-2, 1},
{4, -5, 1},
{-8, 20, -9, 1},
{16, -78,59, -14, 1},
{-32, 324, -360, 135, -20, 1},
{64, -1520, 2254, -1165, 265, -27, 1},
{-128, 8336, -15232, 9954, -3045, 469, -35, 1},
{256, -53872, 113868, -88508, 33649, -6888, 770, -44, 1},
{-512, 405600, -948840, 839684, -376278, 95025, -14028, 1194, -54, 1},
{1024, -3492416, 8793216, -8592220,4373060, -1297569, 235473, -26370, 1770, -65, 1}
		

Crossrefs

Programs

  • Maple
    R := proc(n) add((-1)^k*binomial(n,k)* k!*2^(n-k)*binomial(-x, k), k=0..n);
    expand(%) end: p := n -> seq((-1)^(n-k)*coeff(R(n), x, k), k=0..n):
    seq(p(n), n = 0..9);
    # Or:
    egf := exp(-2*t)*(1+t)^x: ser := series(egf, t, 12): p := n -> coeff(ser, t, n):
    seq(n!*seq(coeff(p(n), x, k), k=0..n), n=0..9); # Peter Luschny, Oct 27 2019
  • Mathematica
    Ca[x, 0] = 1; Ca[x, 1] = -2 + x;
    Ca[x_, n_] := Ca[x, n] = (x - n - 1) Ca[x, n - 1] - 2 (n - 1) Ca[x, n - 2];
    Table[CoefficientList[Ca[x, n], x], {n, 0, 9}] // Flatten
    (* The unsigned row polynomials (see Peter Bala's comment) are: *)
    R[n_] := HypergeometricU[-n, 1 - n - x, 2];
    Table[R[n], {n, 0, 6}] (* Peter Luschny, Oct 27 2019 *)

Formula

T(n, k) = n!*[x^k] p(n) where p(n) = [t^n] exp(-2*t)*(1+t)^x.
With p(0, x) = 1 and p(1, x) = x - 2 the polynomials obey the recurrence
p(n, x) = (x - n - 1)*p(n-1, x) - 2*(n - 1)*p(n-2, x).
Row sums are (-2)^n*(n-1) = (-1)^n*A159964(n-1).
From Peter Bala, Oct 23 2019: (Start)
The unsigned row polynomials are
R(n,x) = Sum_{k=0..n} (-1)^k*binomial(n, k)*k!*2^(n-k)*binomial(-x, k).
They occur in series acceleration formulas for the constant
1/e^2 = n!*2^n*Sum_{k >= 0}(-2)^k/(k!*R(n,k)*R(n,k+1)) = 0.1353 35283 23661 ... (cf. A092553, A046716, A094816).
(End)
R(n, x) = KummerU(-n, 1 - n - x, 2). - Peter Luschny, Oct 27 2019

Extensions

Edited by Peter Luschny, Oct 27 2019

A124791 Row sums of number triangle A124790.

Original entry on oeis.org

1, 1, 1, 3, 5, 13, 29, 73, 181, 465, 1205, 3171, 8425, 22597, 61073, 166195, 454949, 1251985, 3461573, 9611191, 26787377, 74916661, 210178457, 591347989, 1668172841, 4717282753, 13369522249, 37970114703, 108045430901
Offset: 0

Views

Author

Paul Barry, Nov 07 2006

Keywords

Comments

Row sums of a generalized Motzkin triangle.
Apparently the Motzkin transform of A105811, after the sign of A105811(1) is negated. - R. J. Mathar, Dec 11 2008
Hankel transform is A159964. - Paul Barry, Apr 28 2009

Crossrefs

Formula

Conjecture: (n+1)*a(n) +(-n+2)*a(n-1) +(-5*n+7)*a(n-2) +3*(-n+2)*a(n-3) = 0. - R. J. Mathar, Dec 02 2014

A172160 a(0)=1. a(n) = 2^(n-2)*(5-n), for n>0.

Original entry on oeis.org

1, 2, 3, 4, 4, 0, -16, -64, -192, -512, -1280, -3072, -7168, -16384, -36864, -81920, -180224, -393216, -851968, -1835008, -3932160, -8388608, -17825792, -37748736, -79691776, -167772160, -352321536, -738197504, -1543503872, -3221225472, -6710886400
Offset: 0

Views

Author

Paul Curtz, Jan 27 2010

Keywords

Comments

The inverse binomial transform is 1,1,0,0,-1,-1,-2,-2,-3,-3 = essentially A168050 or the negative of A004526.

Examples

			G.f. = 1 + 2*x + 3*x^2 + 4*x^3 + 4*x^4 - 16*x^6 - 64*x^7 + ... - _Michael Somos_, Apr 22 2022
		

Crossrefs

Programs

  • Mathematica
    Table[2^(n-2)*(5-n) -(1/4)*Boole[n==0], {n,0,40}] (* G. C. Greubel, Apr 21 2022 *)
  • SageMath
    [2^(n-2)*(5-n) -(1/4)*bool(n==0) for n in (1..40)] # G. C. Greubel, Apr 21 2022

Formula

a(n+1) - 2*a(n) = -A131577(n).
a(n) + A001787(n-1) = A000079(n+1).
a(n+5) = -A059165(n) = 4*A159964(n+1).
G.f.: (1 - 2*x - x^2)/(1-2*x)^2. - R. J. Mathar, Feb 11 2010
a(n) = 4*a(n-1) - 4*a(n-2), n>2.
E.g.f.: (1/4)*((5-2*x)*exp(2*x) - 1). - G. C. Greubel, Apr 21 2022
a(n) = 4^n*A045891(1-n) if n>1. - Michael Somos, Apr 22 2022

Extensions

Definition replaced with closed form by R. J. Mathar, Feb 11 2010

A232774 Triangle T(n,k), read by rows, given by T(n,0)=1, T(n,1)=2^(n+1)-n-2, T(n,n)=(-1)^(n-1) for n > 0, T(n,k)=T(n-1,k)-T(n-1,k-1) for 1 < k < n.

Original entry on oeis.org

1, 1, 1, 1, 4, -1, 1, 11, -5, 1, 1, 26, -16, 6, -1, 1, 57, -42, 22, -7, 1, 1, 120, -99, 64, -29, 8, -1, 1, 247, -219, 163, -93, 37, -9, 1, 1, 502, -466, 382, -256, 130, -46, 10, -1, 1, 1013, -968, 848, -638, 386, -176, 56, -11, 1, 2036, -1981, 1816, -1486, 1024
Offset: 0

Views

Author

Philippe Deléham, Nov 30 2013

Keywords

Comments

Row sums are A000079(n) = 2^n.
Diagonal sums are A024493(n+1) = A130781(n).
Sum_{k=0..n} T(n,k)*x^k = -A003063(n+2), A159964(n), A000012(n), A000079(n), A001045(n+2), A056450(n), (-1)^(n+1)*A232015(n+1) for x = -2, -1, 0, 1, 2, 3, 4 respectively.

Examples

			Triangle begins:
  1;
  1,    1;
  1,    4,   -1;
  1,   11,   -5,   1;
  1,   26,  -16,   6,   -1;
  1,   57,  -42,  22,   -7,   1;
  1,  120,  -99,  64,  -29,   8,   -1;
  1,  247, -219, 163,  -93,  37,   -9,  1;
  1,  502, -466, 382, -256, 130,  -46, 10,  -1;
  1, 1013, -968, 848, -638, 386, -176, 56, -11, 1;
		

Crossrefs

Formula

G.f.: Sum_{n>=0, k=0..n} T(n,k)*y^k*x^n=(1+2*(y-1)*x)/((1-2*x)*(1+(y-1)*x)).
|T(2*n,n)| = 4^n = A000302(n).
T(n,k) = (-1)^(k-1) * (Sum_{i=0..n-k} (2^(i+1)-1) * binomial(n-i-1,k-1)) for 0 < k <= n and T(n,0) = 1 for n >= 0. - Werner Schulte, Mar 22 2019
Showing 1-5 of 5 results.