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 13 results. Next

A001025 Powers of 16: a(n) = 16^n.

Original entry on oeis.org

1, 16, 256, 4096, 65536, 1048576, 16777216, 268435456, 4294967296, 68719476736, 1099511627776, 17592186044416, 281474976710656, 4503599627370496, 72057594037927936, 1152921504606846976, 18446744073709551616, 295147905179352825856, 4722366482869645213696, 75557863725914323419136, 1208925819614629174706176
Offset: 0

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Author

Keywords

Comments

Same as Pisot sequences E(1, 16), L(1, 16), P(1, 16), T(1, 16). Essentially same as Pisot sequences E(16, 256), L(16, 256), P(16, 256), T(16, 256). See A008776 for definitions of Pisot sequences.
Convolution-square (auto-convolution) of A098430. - R. J. Mathar, May 22 2009
Subsequence of A161441: A160700(a(n)) = 1. - Reinhard Zumkeller, Jun 10 2009
The compositions of n in which each natural number is colored by one of p different colors are called p-colored compositions of n. For n >= 1, a(n) equals the number of 16-colored compositions of n such that no adjacent parts have the same color. - Milan Janjic, Nov 17 2011

References

  • 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

Partial sums give A131865.

Programs

Formula

G.f.: 1/(1-16*x).
E.g.f.: exp(16*x).
From Muniru A Asiru, Nov 07 2018: (Start)
a(n) = 16^n.
a(0) = 1, a(n) = 16*a(n-1). (End)
a(n) = 4^A005843(n) = 2^A008586(n) = A000302(n)^2 = A000079(n)*A001018(n). - Muniru A Asiru, Nov 10 2018
a(n) = ( Sum_{k = 0..n} (2*k + 1)*binomial(2*n + 1, n - k) ) * ( Sum_{k = 0..n} (-1)^k/(2*k + 1)*binomial(2*n + 1, n - k) ). - Peter Bala, Feb 12 2019
a(n) = Sum_{k = 0..2*n} A000984(k) * A000984(2*n-k). - Peter Bala, Aug 23 2025

A386811 a(n) = Sum_{k=0..n} binomial(4*n+1,k).

Original entry on oeis.org

1, 6, 46, 378, 3214, 27896, 245506, 2182396, 19548046, 176142312, 1594831736, 14497410186, 132224930146, 1209397179048, 11088872706188, 101890087382168, 937973964234638, 8649109175873288, 79872298511230120, 738583466508887304, 6837944227813170424
Offset: 0

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Author

Seiichi Manyama, Aug 03 2025

Keywords

Crossrefs

Programs

  • Magma
    [&+[Binomial(4*n+1, k): k in [0..n]]: n in [0..25]]; // Vincenzo Librandi, Aug 21 2025
  • Mathematica
    Table[Sum[Binomial[4*n+1,k], {k, 0, n}], {n, 0, 20}] (* Vaclav Kotesovec, Aug 07 2025 *)
  • PARI
    a(n) = sum(k=0, n, binomial(4*n+1, k));
    

Formula

a(n) = [x^n] 1/((1-2*x) * (1-x)^(3*n+1)).
a(n) = Sum_{k=0..n} 2^(n-k) * binomial(3*n+k,k).
D-finite with recurrence +645*n*(3*n-1)*(3*n-2)*a(n) +8*(-56722*n^3+213090*n^2-305978*n+150255)*a(n-1) +128*(62908*n^3-282348*n^2+385070*n-126735)*a(n-2) +12288*(-2486*n^3+8918*n^2+758*n-18935)*a(n-3) -2949120*(2*n-7)*(4*n-13)*(4*n-11)*a(n-4)=0. - R. J. Mathar, Aug 03 2025
a(n) = 2^(4*n+1) - binomial(4*n+1, n)*(hypergeom([1, -1-3*n], [1+n], -1) - 1). - Stefano Spezia, Aug 05 2025
a(n) = Sum_{k=0..n} 2^k * (-1)^(n-k) * binomial(4*n+1,k) * binomial(4*n-k,n-k). - Seiichi Manyama, Aug 07 2025
a(n) ~ 2^(8*n + 3/2) / (sqrt(Pi*n) * 3^(3*n + 1/2)). - Vaclav Kotesovec, Aug 07 2025
G.f.: g^2/((2-g) * (4-3*g)) where g = 1+x*g^4 is the g.f. of A002293. - Seiichi Manyama, Aug 12 2025
G.f.: B(x)^2/(1 + (B(x)-1)/2), where B(x) is the g.f. of A005810. - Seiichi Manyama, Aug 15 2025
G.f.: 1/(1 - x*g^2*(8-2*g)) where g = 1+x*g^4 is the g.f. of A002293. - Seiichi Manyama, Aug 16 2025

A216702 a(n) = Product_{k=1..n} (16 - 4/k).

Original entry on oeis.org

1, 12, 168, 2464, 36960, 561792, 8614144, 132903936, 2060011008, 32044615680, 499896004608, 7816555708416, 122459372765184, 1921670157238272, 30197673899458560, 475110069351481344, 7482983592285831168, 117967035454858985472, 1861257670509997326336
Offset: 0

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Author

Michel Lagneau, Sep 16 2012

Keywords

Comments

This sequence is generalizable: Product_{k=1..n} (q^2 - q/k) = (q^n/n!) * Product_{k=0..n-1} (q*k + q-1) = expansion of (1- x*q^2)^((1-q)/q).

Crossrefs

Programs

  • Maple
    seq(product(16-4/k, k=1.. n), n=0..20);
    seq((4^n/n!)*product(4*k+3, k=0.. n-1), n=0..20);
  • Mathematica
    Table[Product[16-4/k,{k,n}],{n,0,20}] (* or *) CoefficientList[ Series[ 1/(1-16*x)^(3/4),{x,0,20}],x] (* Harvey P. Dale, Sep 19 2012 *)

Formula

G.f.: 1/(1-16*x)^(3/4). - Harvey P. Dale, Sep 19 2012
From Peter Bala, Sep 24 2023: (Start)
a(n) = 16^n * binomial(n - 1/4, n).
P-recursive: a(n) = 4*(4*n - 1)/n * a(n-1) with a(0) = 1. (End)
From Peter Bala, Mar 31 2024: (Start)
a(n) = (-16)^n * binomial(-3/4, n).
a(n) ~ 1/Gamma(3/4) * 16^n/n^(1/4).
E.g.f.: hypergeom([3/4], [1], 16*x).
a(n) = (16^n)*Sum_{k = 0..2*n} (-1)^k*binomial(-3/4, k)* binomial(-3/4, 2*n - k).
(16^n)*a(n) = Sum_{k = 0..2*n} (-1)^k*a(k)*a(2*n-k).
Sum_{k = 0..n} a(k)*a(n-k) = (16^n)/(2*n)! * Product_{k = 1..n} (4*k^2 - 1) = (16^n)/(2*n)! * A079484(n). (End)

A244038 a(n) = 4^n * binomial(3*n/2,n).

Original entry on oeis.org

1, 6, 48, 420, 3840, 36036, 344064, 3325608, 32440320, 318704100, 3148873728, 31256180280, 311452237824, 3113596420200, 31213674823680, 313672599360720, 3158823892156416, 31870058661517860, 322076161553203200, 3259691964853493400, 33034843349204336640, 335189468043077792760
Offset: 0

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Author

N. J. A. Sloane, Jun 28 2014

Keywords

Crossrefs

Programs

  • Magma
    [Round(4^n*Gamma(3*n/2+1)/(Gamma(n+1)*Gamma(n/2+1))): n in [0..40]]; // G. C. Greubel, Aug 06 2018
  • Maple
    f1:=n->4^n*binomial(3*n/2,n); [seq(f1(n),n=0..40)];
  • Mathematica
    Table[4^n Binomial[3 n/2, n], {n, 0, 40}] (* Vincenzo Librandi, Jun 29 2014 *)
  • PARI
    {a(n) = if( n<1, n==0, 3^n * polcoeff( serreverse( x / (x+1) / 2 * sqrt((x+3) / (x+1) / 3 + x * O(x^n))), n))}; /* Michael Somos, Jan 27 2018 */
    

Formula

a(n) = A045741(n+1) + A244039(n) [Gessel].
a(n) = [x^n] 1/sqrt(1 - 4*x)^(n+2). - Ilya Gutkovskiy, Oct 10 2017
G.f. A(x) satisfies: A(x)^3 * (1 - 108*x^2) = 3*A(x) - 2. - Michael Somos, Jan 27 2018
a(n) = [x^n] ( (1 + 4*x)^(3/2) )^n. It follows that the Gauss congruences a(n*p^k) == a(n*p^(k-1)) (mod p^k) hold for all primes p and positive integers n and k. - Peter Bala, Mar 05 2022
G.f.: 2/(1-2*sin(arcsin(216*x^2-1)/3)). - Vladimir Kruchinin, Oct 06 2022
G.f.: ((3^(5/6)*i + 3^(1/3))*(-18*i*z + sqrt(-324*z^2 + 3))^(1/3) - (3^(5/6)*i - 3^(1/3))*(18*i*z + sqrt(-324*z^2 + 3))^(1/3))/(2*sqrt(-324*z^2 + 3)), where i = sqrt(-1) is the imaginary unit. - Karol A. Penson, Oct 24 2024
From Seiichi Manyama, Aug 07 2025: (Start)
a(n) = Sum_{k=0..n} binomial(3*n+1,k) * binomial(2*n-k,n-k).
a(n) = [x^n] (1+x)^(3*n+1)/(1-x)^(n+1).
a(n) = [x^n] 1/((1-x) * (1-2*x))^(n+1).
a(n) = Sum_{k=0..n} 2^k * (-1)^(n-k) * binomial(3*n+1,k) * binomial(2*n-k,n-k).
a(n) = Sum_{k=0..n} 2^k * binomial(n+k,k) * binomial(2*n-k,n-k). (End)

A034385 Expansion of (1-16*x)^(-1/4), related to quartic factorial numbers.

Original entry on oeis.org

1, 4, 40, 480, 6240, 84864, 1188096, 16972800, 246105600, 3609548800, 53421322240, 796463349760, 11946950246400, 180123249868800, 2727580640870400, 41459225741230080, 632253192553758720
Offset: 0

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Author

Keywords

Crossrefs

Cf. A007696.
Expansion of (1-b^2*x)^(-1/b): A000984 (b=2), A004987 (b=3), this sequence (b=4), A034688 (b=5), A004993 (b=6), A034835 (b=7), A034977 (b=8), A035024 (b=9), A035308 (b=10).

Programs

  • Mathematica
    CoefficientList[Series[1/Surd[1-16x,4],{x,0,20}],x] (* Harvey P. Dale, Aug 06 2018 *)

Formula

a(n) = (4^n/n!)*A007696(n), n >= 1, a(0) := 1, A007696(n) = (4*n-3)!^4 := Product_{j = 1..n} 4*j - 3.
G.f.: (1 - 16*x)^(-1/4).
D-finite with recurrence: n*a(n) + 4*(-4*n + 3)*a(n-1) = 0. - R. J. Mathar, Jan 28 2020
From Peter Bala, Mar 31 2024: (Start)
a(n) = (-16)^n*binomial(-1/4, n).
a(n) ~ Gamma(3/4)/(sqrt(2)*Pi) * 16^n/n^(3/4).
E.g.f.: hypergeom([1/4], [1], 16*x).
a(n) = (16^n)*Sum_{k = 0..2*n} (-1)^k*binomial(-1/4, k)* binomial(-1/4, 2*n - k).
(16^n)*a(n) = Sum_{k = 0..2*n} (-1)^k*a(k)*a(2*n-k).
Sum_{k = 0..n} a(k)*a(n-k) = (4^n)*binomial(2*n, n) = A098430.
Sum_{k = 0..2*n} a(k)*a(2*n-k) = (16^n)*binomial(4*n, 2*n). (End)

A386897 a(n) = 4^n * binomial(5*n/2,n).

Original entry on oeis.org

1, 10, 160, 2860, 53760, 1040060, 20500480, 409404600, 8255569920, 167718033340, 3427543285760, 70384350760360, 1451115518361600, 30018413447053080, 622759359440486400, 12951795276279787760, 269947721071617638400, 5637113741080428839100
Offset: 0

Views

Author

Seiichi Manyama, Aug 07 2025

Keywords

Crossrefs

Programs

  • Mathematica
    Table[Sum[2^k *(-1)^(n-k)*Binomial[5*n+1, k]*Binomial[2*n-k, n-k], {k, 0, n}], {n, 0, 20}] (* Vaclav Kotesovec, Aug 07 2025 *)
    A386897[n_] := 4^n*Binomial[5*n/2, n]; Array[A386897, 20, 0] (* Paolo Xausa, Aug 26 2025 *)
  • PARI
    a(n) = 4^n*binomial(5*n/2, n);

Formula

a(n) == 0 (mod 10) for n > 0.
a(n) = Sum_{k=0..n} binomial(5*n+1,k) * binomial(4*n-k,n-k).
a(n) = [x^n] (1+x)^(5*n+1)/(1-x)^(3*n+1).
a(n) = [x^n] 1/((1-x)^(n+1) * (1-2*x)^(3*n+1)).
a(n) = Sum_{k=0..n} 2^k * (-1)^(n-k) * binomial(5*n+1,k) * binomial(2*n-k,n-k).
a(n) = Sum_{k=0..n} 2^k * binomial(3*n+k,k) * binomial(2*n-k,n-k).
a(n) = [x^n] 1/(1-4*x)^(3*n/2+1).
a(n) = [x^n] (1+4*x)^(5*n/2).
a(n) ~ 2^(n - 1/2) * 5^((5*n+1)/2) / (sqrt(Pi*n) * 3^((3*n+1)/2)). - Vaclav Kotesovec, Aug 07 2025
D-finite with recurrence 3*n*(n-1)*(3*n-4) *(3*n-2)*a(n) -20*(5*n-4) *(5*n-8)*(5*n-2) *(5*n-6)*a(n-2)=0. - R. J. Mathar, Aug 21 2025
O.g.f.: hypergeom([1/5, 2/5, 3/5, 4/5], [1/3, 1/2, 2/3], (12500*x^2)/27) + 10*x*hypergeom([7/10, 9/10, 11/10, 13/10], [5/6, 7/6, 3/2], (12500*x^2)/27). - Karol A. Penson, Aug 26 2025

A249308 Central terms of triangle A249307.

Original entry on oeis.org

1, 2, 8, 16, 96, 192, 1280, 2560, 17920, 35840, 258048, 516096, 3784704, 7569408, 56229888, 112459776, 843448320, 1686896640, 12745441280, 25490882560, 193730707456, 387461414912, 2958796259328, 5917592518656, 45368209309696, 90736418619392, 697972450918400
Offset: 0

Views

Author

Reinhard Zumkeller, Nov 14 2014

Keywords

Comments

a(n) = A128014(n) * 2^n = A249307(n,n);
A098430(n) = a(2*n).

Crossrefs

Programs

  • Haskell
    a249308 n = a249307 n n

A174301 A symmetrical triangle: T(n,k) = binomial(n, k)*if(floor(n/2) greater than or equal to k then 4^k, otherwise 4^(n-k)).

Original entry on oeis.org

1, 1, 1, 1, 8, 1, 1, 12, 12, 1, 1, 16, 96, 16, 1, 1, 20, 160, 160, 20, 1, 1, 24, 240, 1280, 240, 24, 1, 1, 28, 336, 2240, 2240, 336, 28, 1, 1, 32, 448, 3584, 17920, 3584, 448, 32, 1, 1, 36, 576, 5376, 32256, 32256, 5376, 576, 36, 1, 1, 40, 720, 7680, 53760, 258048, 53760, 7680, 720, 40, 1
Offset: 0

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Author

Roger L. Bagula, Mar 15 2010

Keywords

Comments

Row sums are: {1, 2, 10, 26, 130, 362, 1810, 5210, 26050, 76490, ...}.

Examples

			Triangle begins:
  1;
  1,  1;
  1,  8,   1;
  1, 12,  12,    1;
  1, 16,  96,   16,     1;
  1, 20, 160,  160,    20,      1;
  1, 24, 240, 1280,   240,     24,     1;
  1, 28, 336, 2240,  2240,    336,    28,    1;
  1, 32, 448, 3584, 17920,   3584,   448,   32,   1;
  1, 36, 576, 5376, 32256,  32256,  5376,  576,  36,  1;
  1, 40, 720, 7680, 53760, 258048, 53760, 7680, 720, 40,  1;
		

Crossrefs

T(2n,n) gives A098430.

Programs

  • Magma
    [[Floor(n/2) ge k select 4^k*Binomial(n,k) else 4^(n-k)*Binomial(n,k): k in [0..n]]: n in [0..10]]; // G. C. Greubel, Apr 15 2019
    
  • Mathematica
    Table[Binomial[n, m]*If[Floor[n/2]>=m , 4^m, 4^(n-m)], {n,0,10}, {m,0,n} ]//Flatten
  • PARI
    {T(n,k) = binomial(n,k)*if(floor(n/2)>=k, 4^k, 4^(n-k))}; \\ G. C. Greubel, Apr 15 2019
    
  • Sage
    def T(n,k):
       if floor(n/2)>=k: return 4^k*binomial(n,k)
       else: return 4^(n-k)*binomial(n,k)
    [[T(n,k) for k in (0..n)] for n in (0..10)] # G. C. Greubel, Apr 15 2019

Formula

T(n, m) = binomial(n, m)*if(floor(n/2) greater than or equal to m then 4^m, otherwise 4^(n-m)).

Extensions

Edited by G. C. Greubel, Apr 15 2019

A253665 a(n) = 2^n*n!/(floor(n/2)!)^2.

Original entry on oeis.org

1, 2, 8, 48, 96, 960, 1280, 17920, 17920, 322560, 258048, 5677056, 3784704, 98402304, 56229888, 1686896640, 843448320, 28677242880, 12745441280, 484326768640, 193730707456, 8136689713152, 2958796259328, 136104627929088, 45368209309696, 2268410465484800
Offset: 0

Views

Author

Peter Luschny, Feb 01 2015

Keywords

Crossrefs

Programs

  • Maple
    a := n -> 2^n*n!/iquo(n,2)!^2: seq(a(n), n=0..25);
  • Mathematica
    Table[2^n*n!/Floor[n/2]!^2, {n, 0, 25}] (* Michael De Vlieger, Feb 02 2015 *)
    CoefficientList[Series[(1 + 2 (1 - 8 x) x)/(1 - 16 x^2)^(3/2), {x, 0, 20}],x] (* Benedict W. J. Irwin, Aug 15 2016 *)
  • PARI
    a(n)=2^n*n!/(n\2)!^2 \\ Charles R Greathouse IV, Aug 25 2016

Formula

a(n) = 2^n*A056040(n).
a(2*n) = 4^n*C(2*n, n) = A098430(n).
a(n) = sum(k=0..n, C(n,k)*n!/(floor(n/2)!)^2) = sum(k=0..n, A253666(n,k)).
G.f.: (1+2*(1-8*x)*x)/(1-16*x^2)^(3/2). - Benedict W. J. Irwin, Aug 15 2016

A269796 a(n) = 4^n * A000108(n+1).

Original entry on oeis.org

1, 8, 80, 896, 10752, 135168, 1757184, 23429120, 318636032, 4402970624, 61641588736, 872465563648, 12463793766400, 179478630236160, 2602440138424320, 37965009078190080, 556820133146787840, 8205770383215820800, 121445401671594147840, 1804331681977970196480, 26900945076762464747520
Offset: 0

Views

Author

Michel Marcus, Mar 07 2016

Keywords

Crossrefs

Programs

  • Magma
    [4^n*Catalan(n+1): n in [0..25]]; // Vincenzo Librandi, Apr 25 2016
  • Mathematica
    Table[4^n CatalanNumber[n + 1], {n, 0, 20}] (* Bruno Berselli, Mar 07 2016 *)
  • PARI
    cat(n) = binomial(2*n,n)/(n+1);
    a(n) = 4^n*cat(n+1);
    
  • Sage
    [4^n*catalan_number(n+1) for n in (0..20)] # Bruno Berselli, Mar 07 2016
    

Formula

G.f.: (1 - sqrt(1 - 16*x) - 8*x)/(32*x^2). - Bruno Berselli, Mar 07 2016
a(n) = -2^(4*n + 3)*binomial(n + 1/2, -3/2), after Peter Luschny in A000108. - Bruno Berselli, Mar 07 2016
From Amiram Eldar, May 15 2022: (Start)
Sum_{n>=0} 1/a(n) = 52/75 + 512*arcsin(1/4)/(75*sqrt(15)).
Sum_{n>=0} (-1)^n/a(n) = 164/289 + 1536*arcsinh(1/4)/(289*sqrt(17)). (End)
From Karol A. Penson, Aug 26 2025: (Start)
O.g.f.: exp(Sum_{n>=1} A098430(n)*x^n/n).
O.g.f.: exp(Sum_{n>=1} 4^n*(2*n)!*x^n/(n*(n!)^2)).
a(n) = 4^n*binomial(2*n + 2, n + 1)/(n + 2).
a(n) = Integral_{x=0..16} (x^n*sqrt(x)*sqrt(1 - x/16)/(8*Pi)) dx. (End)
Showing 1-10 of 13 results. Next