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.

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A154372 Triangle T(n,k) = (k+1)^(n-k)*binomial(n,k).

Original entry on oeis.org

1, 1, 1, 1, 4, 1, 1, 12, 9, 1, 1, 32, 54, 16, 1, 1, 80, 270, 160, 25, 1, 1, 192, 1215, 1280, 375, 36, 1, 1, 448, 5103, 8960, 4375, 756, 49, 1, 1, 1024, 20412, 57344, 43750, 12096, 1372, 64, 1
Offset: 0

Views

Author

Paul Curtz, Jan 08 2009

Keywords

Comments

From A152650/A152656,coefficients of other exponential polynomials(*). a(n) is triangle A152818 where terms of each column is divided by the beginning one. See A000004, A001787(n+1), A006043=2*A027472, A006044=6*A038846.
(*) Not factorial as written in A006044. See A000110, Bell-Touchard. Second diagonal is 1,4,9,16,25, denominators of Lyman's spectrum of hydrogen, A000290(n+1) which has homogeneous indices for denominators series of Rydberg-Ritz spectrum of hydrogen.
The matrix inverse starts
1;
-1, 1;
3, -4, 1;
-16, 24, -9, 1;
125, -200, 90, -16, 1;
-1296, 2160, -1080, 240, -25, 1;
16807, -28812, 15435, -3920, 525, -36, 1;
.. compare with A122525 (row reversed). - R. J. Mathar, Mar 22 2013
From Peter Bala, Jan 14 2015: (Start)
Exponential Riordan array [exp(z), z*exp(z)]. This triangle is the particular case a = 0, b = 1, c = 1 of the triangle of generalized Stirling numbers of the second kind S(a,b,c) defined in the Bala link. Cf. A059297.
This is the triangle of connection constants when expressing the monomials x^n as a linear combination of the basis polynomials (x - 1)*(x - k - 1)^(k-1), k = 0,1,2,.... For example, from row 3 we have x^3 = 1 + 12*(x - 1) + 9*(x - 1)*(x - 3) + (x - 1)*(x - 4)^2.
Let M be the infinite lower unit triangular array with (n,k)-th entry (k*(n - k + 1) + 1)/(k + 1)*binomial(n,k). M is the row reverse of A145033. For k = 0,1,2,... define M(k) to be the lower unit triangular block array
/I_k 0\
\ 0 M/ having the k X k identity matrix I_k as the upper left block; in particular, M(0) = M. The infinite product M(0)*M(1)*M(2)*..., which is clearly well-defined, is equal to the present triangle. See the Example section. (End)
T(n,k) is also the number of idempotent partial transformations of {1,2,...,n} having exactly k fixed points. - Geoffrey Critzer, Nov 25 2021

Examples

			With the array M(k) as defined in the Comments section, the infinite product M(0)*M(1)*M(2)*... begins
/1      \ /1        \ /1        \      /1        \
|1 1     ||0 1       ||0 1      |      |1  1      |
|1 3 1   ||0 1 1     ||0 0 1    |... = |1  4  1   |
|1 6 5 1 ||0 1 3 1   ||0 0 1 1  |      |1 12  9  1|
|...     ||0 1 6 5 1 ||0 0 1 3 1|      |...       |
|...     ||...       ||...      |      |          |
- _Peter Bala_, Jan 13 2015
		

Crossrefs

Programs

  • Magma
    /* As triangle */ [[(k+1)^(n-k)*Binomial(n,k) : k in [0..n]]: n in [0.. 15]]; // Vincenzo Librandi, Sep 15 2016
  • Mathematica
    T[n_, k_] := (k + 1)^(n - k)*Binomial[n, k]; Table[T[n, k], {n, 0, 10}, {k, 0, n}] // Flatten (* G. C. Greubel, Sep 15 2016 *)

Formula

T(n,k) = (k+1)^(n-k)*binomial(n,k). k!*T(n,k) gives the entries for A152818 read as a triangular array.
E.g.f.: exp(x*(1+t*exp(x))) = 1 + (1+t)*x + (1+4*t+t^2)*x^2/2! + (1+12*t+9*t^2+t*3)*x^3/3! + .... O.g.f.: Sum_{k>=1} (t*x)^(k-1)/(1-k*x)^k = 1 + (1+t)*x + (1+4*t+t^2)*x^2 + .... Row sums are A080108. - Peter Bala, Oct 09 2011
From Peter Bala, Jan 14 2015: (Start)
Recurrence equation: T(n+1,k+1) = T(n,k+1) + Sum_{j = 0..n-k} (j + 1)*binomial(n,j)*T(n-j,k) with T(n,0) = 1 for all n.
Equals the matrix product A007318 * A059297. (End)

A217629 Triangle, read by rows, where T(n,k) = k!*C(n, k)*3^(n-k) for n>=0, k=0..n.

Original entry on oeis.org

1, 3, 1, 9, 6, 2, 27, 27, 18, 6, 81, 108, 108, 72, 24, 243, 405, 540, 540, 360, 120, 729, 1458, 2430, 3240, 3240, 2160, 720, 2187, 5103, 10206, 17010, 22680, 22680, 15120, 5040, 6561, 17496, 40824, 81648, 136080, 181440, 181440, 120960, 40320
Offset: 0

Views

Author

Vincenzo Librandi, Nov 10 2012

Keywords

Comments

Triangle formed by the derivatives of x^n evaluated at x=3.
Sum(T(n,k), k=0..n) = A053486(n) (see the Formula section of A053486). Also:
first column: A000244;
second column: A027471;
third column: 2*A027472;
fourth column: 6*A036216;
fifth column: 24*A036217.

Examples

			Triangle begins:
1;
3,     1;
9,     6,     2;
27,    27,    18,     6;
81,    108,   108,    72,     24;
243,   405,   540,    540,    360,    120;
729,   1458,  2430,   3240,   3240,   2160,    720;
2187,  5103,  10206,  17010,  22680,  22680,   15120,   5040;
6561,  17496, 40824,  81648,  136080, 181440,  181440,  120960,  40320; etc.
		

Crossrefs

Programs

  • Magma
    [Factorial(n)/Factorial(n-k)*3^(n-k): k in [0..n], n in [0..10]];
  • Mathematica
    Flatten[Table[n!/(n-k)!*3^(n-k), {n, 0, 10}, {k, 0, n}]]

Formula

T(n,k) = 3^(n-k)*n!/(n-k)! for n>=0, k=0..n.
E.g.f. (by columns): exp(3x)*x^k.

A318773 Triangle T(n,k) = 3*T(n-1,k) + T(n-4,k-1) for k = 0..floor(n/4), with T(0,0) = 1 and T(n,k) = 0 for n or k < 0, read by rows.

Original entry on oeis.org

1, 3, 9, 27, 81, 1, 243, 6, 729, 27, 2187, 108, 6561, 405, 1, 19683, 1458, 9, 59049, 5103, 54, 177147, 17496, 270, 531441, 59049, 1215, 1, 1594323, 196830, 5103, 12, 4782969, 649539, 20412, 90, 14348907, 2125764, 78732, 540, 43046721, 6908733, 295245, 2835, 1, 129140163, 22320522, 1082565, 13608, 15
Offset: 0

Views

Author

Zagros Lalo, Sep 04 2018

Keywords

Comments

The numbers in rows of the triangle are along a "third layer" skew diagonals pointing top-left in center-justified triangle given in A013610 ((1+3*x)^n) and along a "third layer" skew diagonals pointing top-right in center-justified triangle given in A027465 ((3+x)^n), see links. (Note: First layer of skew diagonals in center-justified triangles of coefficients in expansions of (1+3*x)^n and (3+x)^n are given in A304236 and A304249 respectively.)
The coefficients in the expansion of 1/(1-3*x-x^4) are given by the sequence generated by the row sums.
If s(n) is the row sum at n, then the ratio s(n)/s(n-1) is approximately 3.035744112294..., when n approaches infinity.

Examples

			Triangle begins:
          1;
          3;
          9;
         27;
         81,        1;
        243,        6;
        729,       27;
       2187,      108;
       6561,      405,       1;
      19683,     1458,       9;
      59049,     5103,      54;
     177147,    17496,     270;
     531441,    59049,    1215,     1;
    1594323,   196830,    5103,    12;
    4782969,   649539,   20412,    90;
   14348907,  2125764,   78732,   540;
   43046721,  6908733,  295245,  2835,   1;
  129140163, 22320522, 1082565, 13608,  15;
  387420489, 71744535, 3897234, 61236, 135;
  ...
		

References

  • Shara Lalo and Zagros Lalo, Polynomial Expansion Theorems and Number Triangles, Zana Publishing, 2018, ISBN: 978-1-9995914-0-3.

Crossrefs

Row sums give A052917.
Cf. A000244 (column 0), A027471 (column 1), A027472 (column 2), A036216 (column 3).
Sequences of the form 3^(n-q*k)*binomial(n-(q-1)*k, k): A027465 (q=1), A304249 (q=2), A317497 (q=3), this sequence (q=4).

Programs

  • Magma
    [3^(n-4*k)*Binomial(n-3*k,k): k in [0..Floor(n/4)], n in [0..24]]; // G. C. Greubel, May 12 2021
    
  • Mathematica
    T[n_, k_]:= T[n, k] = 3^(n-4k)*(n-3k)!/((n-4k)! k!); Table[T[n, k], {n, 0, 17}, {k, 0, Floor[n/4]} ]//Flatten
    T[0, 0] = 1; T[n_, k_]:= T[n, k] = If[n<0 || k<0, 0, 3T[n-1, k] + T[n-4, k-1]]; Table[T[n, k], {n, 0, 17}, {k, 0, Floor[n/4]}]//Flatten
  • Sage
    flatten([[3^(n-4*k)*binomial(n-3*k,k) for k in (0..n//4)] for n in (0..24)]) # G. C. Greubel, May 12 2021

Formula

T(n,k) = 3^(n-4*k) * (n-3*k)!/(k! * (n-4*k)!) where n >= 0 and 0 <= k <= floor(n/4).

A094796 Triangle read by rows giving coefficients of polynomials arising in successive differences of central binomial numbers.

Original entry on oeis.org

1, 3, 1, 9, 15, 6, 27, 108, 135, 42, 81, 594, 1539, 1530, 456, 243, 2835, 12555, 25245, 22122, 6120, 729, 12393, 83835, 281475, 482436, 383292, 101520, 2187, 51030, 489888, 2466450, 6916833, 10546200, 7786692, 1980720
Offset: 0

Views

Author

Benoit Cloitre, Jun 11 2004

Keywords

Comments

Let D_0(n)=binomial(2*n,n) and D_{k+1}(n)=D_{k}(n+1)-D_{k}(n); then D_{k}(n)*(n+1)*(n+2)*...*(n+k) = binomial(2*n,n)*P_{k}(n) where P_{k} is a polynomial with integer coefficients of degree k.

Examples

			The third differences of the central binomial numbers are given by D_3(n) = binomial(2*n,n)*(n+1)*(n+2)*(n+3)*(27*n^3 + 108*n^2 + 135*n + 42) and the fourth row of the triangle is 27, 108, 135, 42.
From _M. F. Hasler_, Nov 15 2019: (Start)
The table reads:
  n  |  row(n)
  0  |    1
  1  |    3      1
  2  |    9     15       6
  3  |   27    108     135       42
  4  |   81    594    1539     1530      456
  5  |  243   2835   12555    25245    22122      6120
  6  |  729  12393   83835   281475   482436    383292    101520
  7  | 2187  51030  489888  2466450  6916833  10546200   7786692   1980720
  8  | 6561 201204 2602530 18329976 75981969 186899076 260520300 181218384 44634240
(End)
		

Crossrefs

Cf. A000984 (central binomial coefficients), A163771 (square array of central binomial coefficients and higher differences), A000244 (column k=0).
Main diagonal gives A098461.

Programs

  • Maple
    Dnk := proc(n,k)
        option remember;
        if k < 0 then
            0 ;
        elif k = 0 then
            binomial(2*n,n) ;
        else
            procname(n+1,k-1)-procname(n,k-1) ;
        end if;
    end proc:
    A094796 := proc(n,k)
        local xyvec,i,x ;
        xyvec := [] ;
        for i from 0 to n do
            xyvec := [op(xyvec),[i,Dnk(i,n)*mul(i+j,j=1..n)/Dnk(i,0)]] ;
        end do:
        CurveFitting[PolynomialInterpolation](xyvec,x) ;
        coeff(%,x,n-k) ;
    end proc: # R. J. Mathar, Nov 19 2019
  • Mathematica
    Dnk[n_, k_] := Dnk[n, k] = Which[k < 0, 0, k == 0, Binomial[2*n, n], True, Dnk[n + 1, k - 1] - Dnk[n, k - 1]];
    T[n_, k_] := Module[{xyvec, i, x , ip}, xyvec = {}; For[i = 0, i <= n, i++, AppendTo[xyvec, {i, Dnk[i, n]*Product[i + j, {j, 1, n}]/Dnk[i, 0]}]]; ip = InterpolatingPolynomial[xyvec, x]; Coefficient[ip, x, n - k]];
    Table[T[n, k], {n, 0, 8}, {k, 0, n}] // Flatten (* Jean-François Alcover, Apr 01 2024, after R. J. Mathar *)
  • PARI
    apply( {A094796_row(n,D(n,k)=if(k,D(n+1,k-1)-D(n,k-1),binomial(2*n,n)))=Vec(polinterpolate([0..n],vector(n+1,k,D(k--,n)*(n+k)!/k!/binomial(2*k,k))))}, [0..8]) \\ M. F. Hasler, Nov 15 2019

Formula

T(n,0) = 3^n. T(n,1) = A027472(n+2) + 6*A027472(n+1). T(n,2) = 3*(2*A036217(n-2) + 15*A036217(n-3) + 18*A036217(n-4)). - R. J. Mathar, Nov 19 2019

Extensions

Corrected and edited by M. F. Hasler, following observations by R. J. Mathar and Don Reble, Nov 15 2019
More terms from Don Reble, Nov 15 2019

A082149 A transform of C(n,2).

Original entry on oeis.org

0, 0, 1, 6, 30, 140, 615, 2562, 10220, 39384, 147645, 541310, 1948650, 6908772, 24180611, 83702010, 286978200, 975725744, 3293074233, 11041484022, 36804946550, 122037454140, 402723598431, 1323234680306, 4330586226180
Offset: 0

Views

Author

Paul Barry, Apr 07 2003

Keywords

Comments

Represents the mean of C(n,2) with its second binomial transform. Binomial transform of A080929 (preceded by two zeros).

Crossrefs

Programs

  • Magma
    [Binomial(n,2)*(1 + 3^(n-2))/2: n in [0..30]]; // G. C. Greubel, Feb 10 2018
  • Mathematica
    CoefficientList[Series[(x^2/(1-3*x)^3 + x^2/(1-x)^3)/2, {x,0,50}], x] (* or *) Table[Binomial[n,2]*(1 + 3^(n-2))/2, {n,0,30}] (* G. C. Greubel, Feb 10 2018 *)
    LinearRecurrence[{12,-57,136,-171,108,-27},{0,0,1,6,30,140},30] (* Harvey P. Dale, Aug 11 2021 *)
  • PARI
    for(n=0,30, print1(binomial(n,2)*(1 + 3^(n-2))/2, ", ")) \\ G. C. Greubel, Feb 10 2018
    

Formula

a(n) = C(n, 2)*(3^(n-2) + 1)/2.
G.f.: (x^2/(1-3x)^3+x^2/(1-x)^3)/2.
G.f.: x^2(14*x^3-15*x^2+6*x-1)/((1-x)^3*(3*x-1)^3).
E.g.f.: x^2*exp(2*x)*cosh(x)/2.

A082151 A transform of C(n,2).

Original entry on oeis.org

0, 0, 1, 12, 102, 760, 5295, 35364, 228956, 1445616, 8936685, 54252220, 324214242, 1911205608, 11132579003, 64170616020, 366497915640, 2076171038176, 11676266706969, 65242364726124, 362433045180830, 2002838101907160, 11015341078090503, 60321223747375492
Offset: 0

Views

Author

Paul Barry, Apr 07 2003

Keywords

Comments

Represents the mean of the second and fourth binomial transforms of C(n,2). Binomial transform of A082150

Crossrefs

Programs

  • Magma
    [Binomial(n,2)*(3^(n-2) + 5^(n-2))/2: n in [0..30]]; // G. C. Greubel, Feb 10 2018
  • Mathematica
    CoefficientList[Series[(x^2/(1-5*x)^3 + x^2/(1-3*x)^3)/2, {x,0,50}], x] (* or *) Table[Binomial[n,2]*(3^(n-2) + 5^(n-2))/2, {n,0,30}] (* G. C. Greubel, Feb 10 2018 *)
    LinearRecurrence[{24,-237,1232,-3555,5400,-3375},{0,0,1,12,102,760},30] (* Harvey P. Dale, Apr 10 2023 *)
  • PARI
    for(n=0,30, print1(binomial(n,2)*(3^(n-2) + 5^(n-2))/2, ", ")) \\ G. C. Greubel, Feb 10 2018
    

Formula

a(n) = C(n, 2)*(3^(n-2) + 5^(n-2))/2.
G.f.: (x^2/(1-5*x)^3 + x^2/(1-3*x)^3)/2.
a(n) = x^2*(76*x^3 - 51*x^2 + 12*x - 1)/((1-3*x)^3*(5*x-1)^3).
E.g.f.: x^2*exp(4*x)*cosh(x)/2.

A116138 a(n) = 3^n * n*(n + 1).

Original entry on oeis.org

0, 6, 54, 324, 1620, 7290, 30618, 122472, 472392, 1771470, 6495390, 23383404, 82904796, 290166786, 1004423490, 3443737680, 11708708112, 39516889878, 132497807238, 441659357460, 1464449448420, 4832683179786, 15878816162154
Offset: 0

Views

Author

Mohammad K. Azarian, Apr 08 2007

Keywords

Crossrefs

Programs

Formula

From R. J. Mathar, Dec 19 2008: (Start)
G.f.: 6*x/(1-3*x)^3.
a(n) = 6 * A027472(n+2). (End)
a(n) = 9*a(n-1) -27*a(n-2) +27*a(n-3). - Vincenzo Librandi, Feb 28 2013
E.g.f.: 3*x*(2 + 3*x)*exp(3*x). - G. C. Greubel, May 10 2019
From Amiram Eldar, Jul 20 2020: (Start)
Sum_{n>=1} 1/a(n) = 1 - 2*log(3/2).
Sum_{n>=1} (-1)^(n+1)/a(n) = 4*log(4/3) - 1. (End)

A153703 Partial sums of A069996.

Original entry on oeis.org

1, 13, 94, 526, 2551, 11299, 47020, 186988, 718429, 2686729, 9831658, 35340826, 125154355, 437641663, 1513809688, 5187129880, 17627632249, 59469045061, 199327841590, 664232428390, 2201904349231, 7264715299483, 23865295832644, 78091766836996
Offset: 1

Views

Author

Bruno Berselli, Dec 12 2010

Keywords

Comments

The first differences are in the third row of the square array of A072590.
The general formula for the partial sums of the sequence 1, 4*m, 9*m^2, 16*m^3, 25*m^4,...,n^2*m^(n-1),... is (n^2*m^(n+2)-(2*n*(n+1)-1)*m^(n+1)+(n+1)^2*m^n-m-1)/(m-1)^3 with m>1 (see also References).

References

  • "Supplemento al Periodico di Matematica", Raffaello Giusti Editore (Livorno) - Apr / May, 1913 - p. 99 (Problem 1277, case x=3).

Crossrefs

Programs

  • Magma
    [(3^n*(n^2-n+1)-1)/2: n in [1..25]]; // Vincenzo Librandi, Aug 19 2013
  • Mathematica
    CoefficientList[Series[(1 + 3 x) / ((1 - x) (1 - 3 x)^3), {x, 0, 25}], x] (* Vincenzo Librandi, Aug 19 2013 *)
  • PARI
    a(n) = (3^n*(n^2-n+1)-1)/2 \\ Michel Marcus, Jun 07 2013
    

Formula

a(n) = (3^n*(n^2 - n + 1) - 1)/2.
G.f.: x*(1+3*x)/((1-x)*(1-3*x)^3).
a(n) = 10*a(n-1) - 36*a(n-2) + 54*a(n-3) - 27a(n-4) for n>4.
a(n) = 9*A027472(n+1) + A003462(n) for n>2.
E.g.f.: (1/2)*((1 + 9*x^2)*exp(x) - exp(-x))*exp(2*x). - G. C. Greubel, Aug 24 2016

A367591 Expansion of 1/((1-x) * (1-3*x)^3).

Original entry on oeis.org

1, 10, 64, 334, 1549, 6652, 27064, 105796, 401041, 1483606, 5380840, 19198306, 67559437, 234963352, 808919632, 2760370984, 9346519297, 31429487170, 105039380080, 349114288150, 1154561484781, 3801030845140, 12462203297224, 40705156945324, 132494756301649
Offset: 0

Views

Author

Seiichi Manyama, Nov 24 2023

Keywords

Crossrefs

Partial sums of A027472.

Programs

  • PARI
    a(n) = ((2*n^2+4*n+3)*3^(n+1)-1)/8;

Formula

a(n) = ((2*n^2+4*n+3) * 3^(n+1) - 1)/8.

A126177 Triangle read by rows: T(n,k) is number of hex trees with n edges and k leaves (n >= 1, 1 <= k <= 1 + floor(n/2)).

Original entry on oeis.org

3, 9, 1, 27, 9, 81, 54, 2, 243, 270, 30, 729, 1215, 270, 5, 2187, 5103, 1890, 105, 6561, 20412, 11340, 1260, 14, 19683, 78732, 61236, 11340, 378, 59049, 295245, 306180, 85050, 5670, 42, 177147, 1082565, 1443420, 561330, 62370, 1386, 531441, 3897234
Offset: 1

Views

Author

Emeric Deutsch, Dec 19 2006

Keywords

Comments

A hex tree is a rooted tree where each vertex has 0, 1, or 2 children and, when only one child is present, it is either a left child, or a middle child, or a right child (name due to an obvious bijection with certain tree-like polyhexes; see the Harary-Read paper).
Also number of hex trees with n edges and k-1 nodes of outdegree 2.
Row n has 1 + floor(n/2) terms.
Sum of terms in row n = A002212(n+1).
T(n,1) = 3^n (A000244).
T(n,2) = A027472(n+1).
Sum_{k=1..1+floor(n/2)} k*T(n,k) = A026375(n).

Examples

			Triangle starts:
    3;
    9,   1;
   27,   9;
   81,  54,   2;
  243, 270,  30;
		

Crossrefs

Programs

  • Maple
    T:=(n,k)->3^(n-2*k+2)*binomial(2*k-2,k-1)*binomial(n,2*k-2)/k: for n from 1 to 13 do seq(T(n,k),k=1..1+floor(n/2)) od; # yields sequence in triangular form

Formula

T(n,k) = 3^(n-2k+2)*binomial(2k-2,k-1)*binomial(n,2k-2)/k. Proof: There are Catalan(k-1) full binary trees with k leaves. Each of them has 2k-2 edges. Additional n-2k+2 edges can be inserted as paths at the existing 2k-1 vertices in 3^(n-2k+2)*binomial(n,2k-2) ways.
G.f.: G=G(t,z) satisfies z^2*G^2-(1-3z-2tz^2)G+tz(3+tz)=0.
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