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 1-4 of 4 results.

A049330 Numerator of (1/Pi)*Integral_{x=0..oo} (sin(x)/x)^n dx.

Original entry on oeis.org

1, 1, 3, 1, 115, 11, 5887, 151, 259723, 15619, 381773117, 655177, 20646903199, 27085381, 467168310097, 2330931341, 75920439315929441, 12157712239, 5278968781483042969, 37307713155613, 9093099984535515162569, 339781108897078469, 168702835448329388944396777
Offset: 1

Views

Author

N. J. A. Sloane, Mark S. Riggs (msr1(AT)ra.msstate.edu), Dec 11 1999

Keywords

Examples

			1/2, 1/2, 3/8, 1/3, 115/384, 11/40, ...
		

References

  • Steven R. Finch, Mathematical Constants, Encyclopedia of Mathematics and its Applications, vol. 94, Cambridge University Press, 2003, Section 1.4.3, p. 22.

Crossrefs

Cf. Same as A002297 except for n=4 term, A049331.

Programs

  • Magma
    [Numerator( (1/(2^n*Factorial(n-1)))*(&+[(-1)^j*Binomial(n,j)*(n-2*j)^(n-1): j in [0..Floor(n/2)]]) ): n in [1..25]]; // G. C. Greubel, Apr 01 2022
    
  • Mathematica
    Numerator[Table[Integrate[(Sin[x]/x)^n,{x,0,\[Infinity]}]/Pi,{n,25}]] (* Harvey P. Dale, Jan 01 2013 *)
    Numerator@Table[Sum[(-1)^k (n-2k)^(n-1) Binomial[n, k], {k, 0, n/2}]/((n-1)! 2^n), {n, 1, 30}] (* Vladimir Reshetnikov, Sep 02 2016 *)
  • Sage
    [numerator( (1/(2^n*factorial(n-1)))*sum((-1)^j*binomial(n,j)*(n-2*j)^(n-1) for j in (0..(n//2))) ) for n in (1..25)] # G. C. Greubel, Apr 01 2022

Formula

a(n) = numerator( n*A099765(n)/(2^n*(n-1)!) ). - G. C. Greubel, Apr 01 2022

A049331 Denominator of (1/Pi)*Integral_{0..oo} (sin x / x)^n dx.

Original entry on oeis.org

2, 2, 8, 3, 384, 40, 23040, 630, 1146880, 72576, 1857945600, 3326400, 108999475200, 148262400, 2645053931520, 13621608000, 457065319366656000, 75277762560, 33566877054287216640, 243290200817664
Offset: 1

Views

Author

N. J. A. Sloane, Mark S. Riggs (msr1(AT)ra.msstate.edu), Dec 11 1999

Keywords

Examples

			1/2, 1/2, 3/8, 1/3, 115/384, 11/40, ...
		

References

  • Steven R. Finch, Mathematical Constants, Encyclopedia of Mathematics and its Applications, vol. 94, Cambridge University Press, 2003, Section 1.4.3, p. 22.

Crossrefs

Cf. 2*A002298 (except for n=4 term), A049330.

Programs

  • Magma
    [Denominator( (1/(2^n*Factorial(n-1)))*(&+[(-1)^j*Binomial(n,j)*(n-2*j)^(n-1): j in [0..Floor(n/2)]]) ): n in [1..25]]; // G. C. Greubel, Apr 01 2022
    
  • Mathematica
    Table[ 1/Pi*Integrate[Sinc[x]^n, {x, 0, Infinity}] // Denominator, {n, 1, 20}] (* Jean-François Alcover, Dec 02 2013 *)
    Denominator@Table[Sum[(-1)^k (n-2k)^(n-1) Binomial[n, k], {k, 0, n/2}]/((n-1)! 2^n), {n, 1, 30}] (* Vladimir Reshetnikov, Sep 02 2016 *)
  • Sage
    [denominator( (1/(2^n*factorial(n-1)))*sum((-1)^j*binomial(n,j)*(n-2*j)^(n-1) for j in (0..(n//2))) ) for n in (1..25)] # G. C. Greubel, Apr 01 2022

Formula

a(n) = denominator( n*A099765(n)/(2^n*(n-1)!) ). - G. C. Greubel, Apr 01 2022

A155467 Triangle T(n, k) = Eulerian(n+1, k)*Binomial(n+1, k)/(k+1), read by rows.

Original entry on oeis.org

1, 1, 1, 1, 6, 1, 1, 22, 22, 1, 1, 65, 220, 65, 1, 1, 171, 1510, 1510, 171, 1, 1, 420, 8337, 21140, 8337, 420, 1, 1, 988, 40068, 218666, 218666, 40068, 988, 1, 1, 2259, 175296, 1852914, 3935988, 1852914, 175296, 2259, 1, 1, 5065, 717600, 13655760, 55034868, 55034868, 13655760, 717600, 5065, 1
Offset: 0

Views

Author

Roger L. Bagula, Jan 22 2009

Keywords

Comments

The sequence substitutes Eulerian numbers for the binomial in a triangle of Narayana numbers A001263,

Examples

			Triangle begins as:
  1;
  1,    1;
  1,    6,      1;
  1,   22,     22,        1;
  1,   65,    220,       65,        1;
  1,  171,   1510,     1510,      171,        1;
  1,  420,   8337,    21140,     8337,      420,        1;
  1,  988,  40068,   218666,   218666,    40068,      988,      1;
  1, 2259, 175296,  1852914,  3935988,  1852914,   175296,   2259,    1;
  1, 5065, 717600, 13655760, 55034868, 55034868, 13655760, 717600, 5065, 1;
		

Crossrefs

Cf. A001263 (m=0), this sequence (m=1), A155491 (m=3), A155493 (m=4).
Cf. A001263, A008292, A099765 (row sums).

Programs

  • Mathematica
    (* First program *)
    Needs["Combinatorica`"]
    T[n_, k_]:= Eulerian[n+1, k]*Binomial[n+1, k]/(k+1);
    Table[T[n, k], {n,0,10}, {k,0,n}]//Flatten (* Roger L. Bagula, Apr 14 2010 *)
    (* Second program *)
    t[n_, k_, m_]:= t[n,k,m]= If[k==1 || k==n, 1, (m*n-m*k+1)*t[n-1,k-1,m] + (m*k -(m -1))*t[n-1,k,m]];
    T[n_, k_, m_]:= Binomial[n+1,k]*t[n+1,k+1,m]/(k+1);
    Table[T[n,k,1], {n,0,12}, {k,0,n}]//Flatten (* G. C. Greubel, Apr 01 2022 *)
  • Sage
    @CachedFunction
    def t(n,k,m):
        if (k==1 or k==n): return 1
        else: return (m*(n-k)+1)*t(n-1,k-1,m) + (m*k-m+1)*t(n-1,k,m)
    def T(n,k,m): return binomial(n+1,k)*t(n+1,k+1,m)/(k+1)
    flatten([[T(n,k,1) for k in (0..n)] for n in (0..12)]) # G. C. Greubel, Apr 01 2022

Formula

T(n, k) = binomial(n+1, k)*t(n, k, m)/(k+1), where t(n,k,m) = (m*(n-k)+1)*t(n-1,k-1,m) + (m*k-m+1)*t(n-1,k,m), t(n,1,m) = t(n,n,m) = 1, and m = 1.
Sum_{k=0..n} T(n, k) = A099765(n+2).
T(n, k) = Eulerian(n+1, k)*Binomial(n+1, k)/(k+1). - Roger L. Bagula, Apr 14 2010
From G. C. Greubel, Apr 01 2022: (Start)
T(n, k) = binomial(n+1, k)*A008292(n+1, k+1)/(k+1).
T(n, n-k) = T(n, k).
T(n, 1) = A003469(n). (End)

Extensions

Edited by G. C. Greubel, Apr 01 2022

A261398 Integer coefficients arising from a formula for Sum_{m>=1} sin(Pi*m/3)^2/m^2.

Original entry on oeis.org

1, 2, 6, 32, 230, 2112, 23548, 309248, 4675014, 79969280, 1527092468, 32203259904, 743288515164, 18638209056768, 504541774904760, 14664951970922496, 455522635895576646, 15058911973677465600, 527896878148304296900, 19559986314930028544000, 763820398700983273655796, 31353195811771939838492672
Offset: 1

Views

Author

N. J. A. Sloane, Aug 18 2015

Keywords

Crossrefs

Programs

  • Magma
    [(&+[(-1)^j*Binomial(n,j)*(n-2*j)^(n-1): j in [0..Floor(n/2)]]): n in [1..25]]; // G. C. Greubel, Apr 01 2022
    
  • Maple
    A261398 := proc(n)
        add( (-1)^i*binomial(n,i)*(n-2*i)^(n-1),i=0..floor((n-1)/2)) ;
    end proc:
    seq(A261398(n),n=1..25) ; # R. J. Mathar, Aug 19 2015
  • Mathematica
    Table[Sum[(-1)^k (n-2k)^(n-1) Binomial[n, k], {k, 0, n/2}], {n, 1, 20}] (* Vladimir Reshetnikov, Sep 05 2016 *)
  • PARI
    a(n) = sum(i=0, (n-1)\2, (-1)^i*binomial(n,i)*(n-2*i)^(n-1)); \\ Michel Marcus, Sep 05 2016
    
  • Sage
    [sum((-1)^j*binomial(n,j)*(n-2*j)^(n-1) for j in (0..(n//2))) for n in (1..25)] # G. C. Greubel, Apr 01 2022

Formula

a(n) = Sum_{i=0..floor((n-1)/2)} (-1)^i*binomial(n,i)*(n-2*i)^(n-1).
a(n)/(2^n*(n-1)!) = A049330(n)/A049331(n).
a(n) = n * A099765(n). - Vladimir Reshetnikov, Sep 05 2016
Showing 1-4 of 4 results.