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 1-10 of 14 results. Next

A007758 a(n) = 2^n*n^2.

Original entry on oeis.org

0, 2, 16, 72, 256, 800, 2304, 6272, 16384, 41472, 102400, 247808, 589824, 1384448, 3211264, 7372800, 16777216, 37879808, 84934656, 189267968, 419430400, 924844032, 2030043136, 4437573632, 9663676416, 20971520000, 45365592064, 97844723712, 210453397504
Offset: 0

Views

Author

David J. Snook (ua532(AT)freenet.victoria.bc.ca)

Keywords

Comments

"The traveling salesman problem can be solved in time O(n^2 2^n) (where n is the size of the network to visit)." [Wikipedia] - Jonathan Vos Post, Apr 10 2006
Satisfies Benford's law [Theodore P. Hill, Personal communication, Feb 06, 2017]. - N. J. A. Sloane, Feb 08 2017

References

  • Arno Berger and Theodore P. Hill. An Introduction to Benford's Law. Princeton University Press, 2015.
  • Konrad Knopp, Theory and Application of Infinite Series, Dover, p. 269.

Crossrefs

Programs

  • Magma
    [2^n*n^2: n in [0..30]]; // Vincenzo Librandi, Oct 27 2011
    
  • Maple
    seq(seq(k^n*n^k, k=2..2), n=0..25); and seq(2^n*n^2, n=0..25); # Zerinvary Lajos, Jul 01 2007
  • Mathematica
    Table[n^2 * 2^n, {n, 0, 31}] (* Alonso del Arte, Oct 22 2014 *)
    LinearRecurrence[{6,-12,8},{0,2,16},30] (* Harvey P. Dale, Jan 27 2017 *)
  • PARI
    a(n)=n^2<Charles R Greathouse IV, Oct 28 2014

Formula

From Henry Bottomley, Jun 13 2001: (Start)
a(n) = 2*A014477(n-1).
G.f.: 2*x(1+2*x)/(1-2*x)^3.
Binomial transform of A002939.
Inverse binomial transform of A062189. (End)
Sum_{n>=1} 1/a(n) = Pi^2/12 - (1/2)*(log(2))^2. - Benoit Cloitre, Apr 05 2002
a(n) = Sum_{k=1..n} k*2^k. - Zerinvary Lajos, Oct 09 2006
E.g.f.: exp(2*x)*(2*x + 4*x^2). - Geoffrey Critzer, Aug 28 2013
Sum_{n>=1} (-1)^(n+1)/a(n) = -Li_2(-1/2) (A355234). - Amiram Eldar, Jun 28 2022

A118416 Triangle read by rows: T(n,k) = (2*k-1)*2^(n-1), 0 < k <= n.

Original entry on oeis.org

1, 2, 6, 4, 12, 20, 8, 24, 40, 56, 16, 48, 80, 112, 144, 32, 96, 160, 224, 288, 352, 64, 192, 320, 448, 576, 704, 832, 128, 384, 640, 896, 1152, 1408, 1664, 1920, 256, 768, 1280, 1792, 2304, 2816, 3328, 3840, 4352, 512, 1536, 2560, 3584, 4608, 5632, 6656, 7680
Offset: 1

Views

Author

Reinhard Zumkeller, Apr 27 2006

Keywords

Comments

Row sums give A014477: Sum_{k=1..n} T(n,k) = A014477(n-1);
central terms give A118415; T(2*k-1,k) = A058962(k-1);
T(n,1) = A000079(n-1);
T(n,2) = A007283(n-1) for n > 1;
T(n,3) = A020714(n-1) for n > 2;
T(n,4) = A005009(n-1) for n > 3;
T(n,5) = A005010(n-1) for n > 4;
T(n,n-1) = A118417(n-1) for n > 1;
T(n,n) = A014480(n-1) = A118413(n,n);
A001511(T(n,k)) = A002024(n,k);
A003602(T(n,k)) = A002260(n,k).
The alternating row sums, Sum_{k=1..n} (-1)^(k+1)*T(n,k), are: (a) in odd rows, the central term, T(n,(n+1)/2) = A058962((n-1)/2); (b) in even rows, the negation of the average of the two central terms, -(T(2n,n) + T(2n,+1))/2 = -A018215(m/2). The absolute values of the alternating row sums give the plain row means, Sum_{k=1..n} T(n,k)/n; the alternating sign row means are (-2)^(n-1). - Gregory Gerard Wojnar, Feb 10 2024

Examples

			Triangle begins:
   1;
   2,   6;
   4,  12,  20;
   8,  24,  40,  56;
  16,  48,  80, 112, 144;
  32,  96, 160, 224, 288, 352;
  64, 192, 320, 448, 576, 704, 832;
		

Crossrefs

Programs

  • Haskell
    a118416 n k = a118416_tabl !! (n-1) !! (k-1)
    a118416_row 1 = [1]
    a118416_row n = (map (* 2) $ a118416_row (n-1)) ++ [a014480 (n-1)]
    a118416_tabl = map a118416_row [1..]
    -- Reinhard Zumkeller, Jan 22 2012
    
  • Maple
    A118416 := proc(n,k) 2^(n-1)*(2*k-1) ; end proc: # R. J. Mathar, Sep 04 2011
  • Mathematica
    Flatten[Table[(2k-1)2^(n-1),{n,10},{k,n}]] (* Harvey P. Dale, Aug 26 2014 *)
  • Python
    from math import isqrt
    def A118416(n): return (a:=(m:=isqrt(k:=n<<1))+(k>m*(m+1)))*(1-a)+(n<<1)-1<Chai Wah Wu, Jun 20 2025

Formula

T(n,k) = 2*T(n-1,k), 1 <= k < n; T(n,n) = A014480(n-1).

A014479 Exponential generating function = (1+2*x)/(1-2*x)^3.

Original entry on oeis.org

1, 8, 72, 768, 9600, 138240, 2257920, 41287680, 836075520, 18579456000, 449622835200, 11771943321600, 331576403558400, 9998303861145600, 321374052679680000, 10969567664799744000, 396275631890890752000
Offset: 0

Views

Author

Keywords

Crossrefs

Programs

  • Maple
    seq(add(count(Composition(k))*count(Permutation(k)),k=1..n),n=1..17); # Zerinvary Lajos, Oct 17 2006
    seq(2^n*(n+1)^2*n!, n=0..30); # Robert Israel, Oct 28 2015
  • Mathematica
    Table[2^n (n+1)^2 n!, {n, 0, 20}] (* Vladimir Reshetnikov, Oct 28 2015 *)
  • PARI
    {a(n)=polcoeff( sum(m=0,n,(2*m+1)^(m+1)*x^m / (1 + (2*m+1)*x +x*O(x^n))^(m+1)),n)} \\ Paul D. Hanna, Jan 02 2013
    for(n=0,20,print1(a(n),", "))
    
  • PARI
    vector(30, n, n--; n!*(n+1)^2*2^n) \\ Altug Alkan, Oct 28 2015

Formula

a(n) = A014477(n) * n!. - Franklin T. Adams-Watters, Nov 02 2006
G.f.: Sum_{n>=0} (2*n+1)^(n+1) * x^n / (1 + (2*n+1)*x)^(n+1). - Paul D. Hanna, Jan 02 2013
From Vladimir Reshetnikov, Oct 28 2015: (Start)
a(n) = 2^n*(n+1)^2*n!.
Recurrence: a(0) = 1, n*a(n) = 2*(n+1)^2*a(n-1). (End)
From Amiram Eldar, Dec 10 2022: (Start)
Sum_{n>=0} 1/a(n) = 2*(Ei(1/2) - gamma + log(2)), where Ei(x) is the exponential integral and gamma is Euler's constant (A001620).
Sum_{n>=0} (-1)^n/a(n) = 2*(gamma - Ei(-1/2) - gamma - log(2)). (End)

A036826 a(n) = A036800(n)/2.

Original entry on oeis.org

0, 1, 9, 45, 173, 573, 1725, 4861, 13053, 33789, 84989, 208893, 503805, 1196029, 2801661, 6488061, 14876669, 33816573, 76283901, 170917885, 380633085, 843055101, 1858076669, 4076863485, 8908701693, 19394461693, 42077257725, 90999619581, 196226318333
Offset: 0

Views

Author

Keywords

Comments

Binomial transform of A054569 (with leading 0). Partial sums of A014477 (with leading 0). - Paul Barry, Jun 11 2003
This sequence is related to A000337 by a(n) = n*A000337(n) - Sum_{i=0..n-1} A000337(i). - Bruno Berselli, Mar 06 2012

Crossrefs

Programs

  • Magma
    m:=28; R:=PowerSeriesRing(Integers(), m); [0] cat Coefficients(R!((1+2*x)/((1-x)*(1-2*x)^3))); // Bruno Berselli, Mar 06 2012
    
  • Maple
    A036826:= n-> 2^n*(3-2*n+n^2) -3; seq(A036826(n), n=0..30); # G. C. Greubel, Mar 31 2021
  • Mathematica
    LinearRecurrence[{7,-18,20,-8}, {0,1,9,45}, 29] (* Bruno Berselli, Mar 06 2012 *)
  • PARI
    for(n=0, 28, print1(2^n*(n^2-2*n+3)-3", ")); \\ Bruno Berselli, Mar 06 2012
    
  • Sage
    [2^n*(3-2*n+n^2) -3 for n in (0..30)] # G. C. Greubel, Mar 31 2021

Formula

From Paul Barry, Jun 11 2003: (Start)
G.f.: x*(1+2*x)/((1-x)*(1-2*x)^3).
a(n) = 2^n*(n^2-2*n+3) - 3.
a(n) = Sum_{k=0..n} k^2*2^(k-1). (End)
a(n) = 7*a(n-1) -18*a(n-2) +20*a(n-3) -8*a(n-4). - Harvey P. Dale, Mar 04 2015
E.g.f.: -3*exp(x) + (3 -2*x +4*x^2)*exp(2*x). - G. C. Greubel, Mar 31 2021

A118414 a(n) = (2*n - 1) * (2^n - 1).

Original entry on oeis.org

1, 9, 35, 105, 279, 693, 1651, 3825, 8687, 19437, 42987, 94185, 204775, 442341, 950243, 2031585, 4325343, 9175005, 19398619, 40894425, 85983191, 180355029, 377487315, 788529105, 1644167119, 3422552013, 7113539531, 14763950025, 30601641927, 63350767557, 130996502467, 270582939585
Offset: 1

Views

Author

Reinhard Zumkeller, Apr 27 2006

Keywords

Comments

Row sums of triangle A118413.
For fixed n, define a triangle T(r,c) counting down the first n odd numbers on the left side, T(r,1) = 2*(n-r)+1, and counting up odd numbers on the right side, T(r,r) = 2*(n+r)-3, r>1. The interior elements are set by T(r,c)=T(r-1,c-1) + T(r-1,c). The sum of all members in this triangle is a(n). - J. M. Bergot, Oct 12 2012
Row sums of triangle A277046. - Miquel Cerda, Sep 28 2016

Examples

			The triangle T(r,c) for n=4 has row(1)=7; row(2) = 5, 9; row(3) = 3, 14, 11; row(4) = 1, 17, 25, 13, and a sum of 7+5+9+...+13 = 105 = a(4). - _J. M. Bergot_, Oct 12 2012
		

Crossrefs

Programs

  • Magma
    [(2*n-1)*(2^n-1): n in [1..40]]; // Vincenzo Librandi, Dec 26 2010
    
  • Mathematica
    Table[(2 n - 1) (2^n - 1), {n, 32}] (* or *)
    Rest@ CoefficientList[Series[-x (-1 - 3 x + 6 x^2)/((2 x - 1)^2*(x - 1)^2), {x, 0, 32}], x] (* Michael De Vlieger, Sep 26 2016 *)
    LinearRecurrence[{6,-13,12,-4},{1,9,35,105},40] (* Harvey P. Dale, Sep 12 2023 *)
  • PARI
    a(n)=(2*n-1)*(2^n-1) \\ Charles R Greathouse IV, Oct 12 2012

Formula

a(n) = A005408(n-1)*(A000079(n) - 1). Corrected by Omar E. Pol, Sep 26 2016
G.f. -x*(-1-3*x+6*x^2) / ( (2*x-1)^2*(x-1)^2 ). - R. J. Mathar, Oct 15 2012
a(n) = A005408(n-1)*A000225(n). - Miquel Cerda, Sep 26 2016

A086603 a(n) = n^3*3^(n-1).

Original entry on oeis.org

0, 1, 24, 243, 1728, 10125, 52488, 250047, 1119744, 4782969, 19683000, 78594219, 306110016, 1167575877, 4374822312, 16142520375, 58773123072, 211488540273, 753145430616, 2657317134051, 9298091736000, 32291110337661
Offset: 0

Views

Author

Paul Barry, Jul 23 2003

Keywords

Comments

Binomial transform of A086604. Second binomial transform of A086605.

Crossrefs

Programs

  • GAP
    List([0..30], n-> 3^(n-1)*n^3 ); # G. C. Greubel, Feb 08 2020
  • Magma
    [3^(n-1)*n^3: n in [0..30]]; // G. C. Greubel, Feb 08 2020
    
  • Maple
    seq( 3^(n-1)*n^3, n=0..30); # G. C. Greubel, Feb 08 2020
  • Mathematica
    Table[n^3 3^(n-1),{n,0,30}]  (* Harvey P. Dale, Mar 12 2011 *)
  • PARI
    vector(31, n, my(m=n-1); 3^(m-1)*m^3) \\ G. C. Greubel, Feb 08 2020
    
  • Sage
    [3^(n-1)*n^3 for n in (0..30)] # G. C. Greubel, Feb 08 2020
    

Formula

From G. C. Greubel, Feb 08 2020: (Start)
G.f.: x*(1 + 12*x + 9*x^2)/(1-3*x)^4.
E.g.f.: x*(1 + 9*x + 9*x^2)*exp(x). (End)

A141692 Triangle read by rows: T(n,k) = n*(binomial(n - 1, k - 1) - binomial(n - 1, k)), 0 <= k <= n.

Original entry on oeis.org

0, -1, 1, -2, 0, 2, -3, -3, 3, 3, -4, -8, 0, 8, 4, -5, -15, -10, 10, 15, 5, -6, -24, -30, 0, 30, 24, 6, -7, -35, -63, -35, 35, 63, 35, 7, -8, -48, -112, -112, 0, 112, 112, 48, 8, -9, -63, -180, -252, -126, 126, 252, 180, 63, 9, -10, -80, -270, -480, -420, 0, 420, 480, 270, 80, 10
Offset: 0

Views

Author

Roger L. Bagula, Sep 09 2008

Keywords

Comments

The row sums are zero.
Row n consists of the coefficients in the expansion of n*(x - 1)*(x + 1)^(n - 1). - Franck Maminirina Ramaharo, Oct 02 2018

Examples

			Triangle begins:
    0;
   -1,   1;
   -2,   0,    2;
   -3,  -3,    3,    3;
   -4,  -8,    0,    8,    4;
   -5, -15,  -10,   10,   15,   5;
   -6, -24,  -30,    0,   30,  24,   6;
   -7, -35,  -63,  -35,   35,  63,  35,   7;
   -8, -48, -112, -112,    0, 112, 112,  48,   8;
   -9, -63, -180, -252, -126, 126, 252, 180,  63,  9;
  -10, -80, -270, -480, -420,   0, 420, 480, 270, 80, 10;
  ...
		

Crossrefs

Programs

  • Maple
    a:=proc(n,k) n*(binomial(n-1,k-1)-binomial(n-1,k)); end proc: seq(seq(a(n,k),k=0..n),n=0..10); # Muniru A Asiru, Oct 03 2018
  • Mathematica
    Table[Table[n*(Binomial[n - 1, k - 1] - Binomial[n - 1, k]),{k, 0, n}],{n, 0, 12}]//Flatten
  • Maxima
    T(n, k) := n*(binomial(n - 1, k - 1) - binomial(n - 1, k))$
    tabl(nn) := for n:0 thru nn do print(makelist(T(n, k), k, 0, n))$ /* Franck Maminirina Ramaharo, Oct 02 2018 */

Formula

T(n,k) = n*(B(1/2;n-1,k-1) - B(1/2;n-1,k))*2^(n - 1), where B(t;n,k) = binomial(n,k)*t^k*(1 - t)^(n - k) denotes the k-th Benstein basis polynomial of degree n.
T(n,k) = n*A112467(n,k).
From Franck Maminirina Ramaharo, Oct 02 2018: (Start)
T(n,k) = -T(n,n-k)
T(n,0) = -n.
T(n,1) = -A067998(n)
E.g.f.: (x*y - y)/(x*y + y - 1)^2.
Sum_{k=0..n} abs(T(n,k)) = 2*A100071(n).
Sum_{k=0..n} T(n,k)^2 = 2*A037965(n).
Sum_{k=0..n} k*T(n,k) = A001787(n).
Sum_{k=0..n} k^2*T(n,k) = A014477(n-1). (End)

Extensions

Edited, new name and offset corrected by Franck Maminirina Ramaharo, Oct 02 2018

A152548 Sum of squared terms in rows of triangle A152547: a(n) = Sum_{k=0..C(n,[n/2])-1} A152547(n,k)^2.

Original entry on oeis.org

1, 4, 10, 24, 54, 120, 260, 560, 1190, 2520, 5292, 11088, 23100, 48048, 99528, 205920, 424710, 875160, 1798940, 3695120, 7574996, 15519504, 31744440, 64899744, 132503644, 270415600, 551231800, 1123264800, 2286646200, 4653525600
Offset: 0

Views

Author

Paul D. Hanna, Dec 14 2008

Keywords

Crossrefs

Programs

  • Maple
    seq(simplify((-2)^n*hypergeom([-n,3/2], [1], 2)),n=0..29); # Peter Luschny, Apr 26 2016
  • Mathematica
    CoefficientList[Series[Sqrt[(1+2x)/(1-2x)^3],{x,0,30}],x] (* Harvey P. Dale, Jan 04 2016 *)
  • PARI
    a(n)=sum(k=0,floor((n+1)/2),binomial(n+1, k)*(n+1-2*k)^3)/(n+1)

Formula

G.f.: A(x) = sqrt( (1+2x)/(1-2x)^3 ).
a(n) = Sum_{k=0..[(n+1)/2]} C(n+1, k)*(n+1-2k)^3/(n+1).
a(n) = A107233(n)/(n+1).
Self-convolution equals A014477.
E.g.f.: ((1 + 4*x)*BesselI(0, 2*x) + 4*x*BesselI(1, 2*x)). - Peter Luschny, Aug 26 2012
a(n) = (-2)^n*hypergeom([-n,3/2], [1], 2). - Peter Luschny, Apr 26 2016
D-finite with recurrence: (n+1)*a(n+1) = 4*a(n) + 4*n*a(n-1). - Vladimir Reshetnikov, Oct 10 2016
a(n) ~ 2^(n + 3/2) * sqrt(n/Pi). - Vaclav Kotesovec, Oct 11 2016
From Peter Bala, Mar 31 2024: (Start)
a(n) = (2^n) * Sum_{k = 0..n} (-1)^(n+k)*binomial(1/2, k)*binomial(-3/2, n-k).
a(n) = (2^n) * Sum_{k = 0..n} (2^k)*binomial(n, k)*binomial(1/2, k).
a(n) = (2^n)* Sum_{k = 0..n} binomial(n, k)*binomial(k+1/2, n). See A008288.
a(n) = (2*n + 1)!/(2^n * n!^2) * hypergeom([-n, -1/2], [-n-1/2], -1).
a(n) = 2^n * hypergeom([-n, -1/2], [1], 2).
a(n) = (-1/2)^n * binomial(2*n, n)/(1 - 2*n) * hypergeom([-n, 3/2], [-n+3/2], -1).(End)

A084850 2^(n-1)*(n^2+2n+2).

Original entry on oeis.org

1, 5, 20, 68, 208, 592, 1600, 4160, 10496, 25856, 62464, 148480, 348160, 806912, 1851392, 4210688, 9502720, 21299200, 47448064, 105119744, 231735296, 508559360, 1111490560, 2420113408, 5251268608, 11358175232, 24494735360
Offset: 0

Views

Author

Paul Barry, Jun 09 2003

Keywords

Comments

Binomial transform of A084849. a(n)=A014477(n-1)+A001787(n+1).

Crossrefs

Cf. A134083.

Programs

  • Mathematica
    LinearRecurrence[{6,-12,8},{1,5,20},40] (* Harvey P. Dale, Mar 15 2016 *)

Formula

G.f.: (1 - x+2x^2)/(1 - 2x)^3.
Equals A134083 * [1,2,3,...]. - Gary W. Adamson, Oct 07 2007

A135065 A127733 * A007318 as infinite lower triangular matrices.

Original entry on oeis.org

1, 4, 4, 9, 18, 9, 16, 48, 48, 16, 25, 100, 150, 100, 25, 36, 180, 360, 360, 180, 36, 49, 294, 735, 980, 735, 294, 49, 64, 448, 1344, 2240, 2240, 1344, 448, 64, 81, 648, 2268, 4536, 5670, 4536, 2268, 648, 81, 100, 900, 3600, 8400, 12600, 12600, 8400, 3600
Offset: 0

Views

Author

Gary W. Adamson, Nov 16 2007

Keywords

Comments

A135065 * [1/1, 1/2, 1/3, ...] = A066524: (1, 6, 21, 60, 155, ...).
Triangle T(n,k), 0 <= k <= n, read by rows, given by (4, -7/4, 17/28, -32/119, 7/17, 0, 0, 0, 0, 0, 0, 0, ...) DELTA (4, -7/4, 17/28, -32/119, 7/17, 0, 0, 0, 0, 0, 0, 0, ...) where DELTA is the operator defined in A084938. - Philippe Deléham, Oct 27 2011

Examples

			First few rows of the triangle:
   1;
   4,   4;
   9,  18,   9;
  16,  48,  48,  16;
  25, 100, 150, 100,  25;
  36, 180, 360, 360, 180,  36;
  49, 294, 735, 980, 735, 294,  49;
		

Crossrefs

Cf. A000290, A127733, A066524, A014477 (row sums), A084938.

Programs

  • Maple
    with(combstruct):for n from 0 to 11 do seq(n*m*count(Combination(n), size=m), m = 1 .. n) od; # Zerinvary Lajos, Apr 09 2008
  • Mathematica
    Flatten[Table[Binomial[n,k](n+1)^2,{n,0,10},{k,0,n}]] (* Harvey P. Dale, Jul 12 2013 *)

Formula

T(n,k) = binomial(n,k)*(n+1)^2 = A007318(n,k)*A000290(n+1). - Philippe Deléham, Oct 27 2011
T(n-1,k-1) = Sum_{i=-k..k} (-1)^i*(k^2-i^2)*binomial(n,k+i)*binomial(n,k-i). - Mircea Merca, Apr 05 2012
G.f.: (-1 - x - x*y)/(x + x*y - 1)^3. - R. J. Mathar, Aug 12 2015

Extensions

Corrected by Zerinvary Lajos, Apr 09 2008
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