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 1-7 of 7 results.

A094686 A Fibonacci convolution.

Original entry on oeis.org

1, 0, 1, 2, 2, 4, 7, 10, 17, 28, 44, 72, 117, 188, 305, 494, 798, 1292, 2091, 3382, 5473, 8856, 14328, 23184, 37513, 60696, 98209, 158906, 257114, 416020, 673135, 1089154, 1762289, 2851444, 4613732, 7465176, 12078909, 19544084, 31622993, 51167078, 82790070
Offset: 0

Views

Author

Paul Barry, May 19 2004

Keywords

Comments

Convolution of A000045 and A049347.
Diagonal sums of number triangle A116088. - Paul Barry, Feb 04 2006
Let (b(n)) be the p-INVERT of (1,1,0,0,0,0,0,0,...) using p(S) = 1 - S^2; then b(n) = a(n+1) for n >=0. See A292324. - Clark Kimberling, Sep 15 2017

Crossrefs

Programs

  • Magma
    [(Fibonacci(n+1) +((n+2) mod 3) -1)/2: n in [0..40]]; // G. C. Greubel, Feb 09 2023
    
  • Mathematica
    LinearRecurrence[{0,1,2,1}, {1,0,1,2}, 40] (* Jean-François Alcover, Sep 21 2017 *)
  • PARI
    Vec(1/((1-x-x^2)*(1+x+x^2)) + O(x^50)) \\ Michel Marcus, Sep 27 2014
    
  • SageMath
    [(fibonacci(n+1) + (n+2)%3 - 1)/2 for n in range(41)] # G. C. Greubel, Feb 09 2023

Formula

G.f.: 1/((1-x-x^2)*(1+x+x^2)).
a(n) = 2*sqrt(3)*Sum_{k=0..n} Fibonacci(k+1)*cos((4*(n-k)+1)*Pi/6)/3.
a(n) = a(n-2) + 2*a(n-3) + a(n-4).
From Paul Barry, Jan 13 2005: (Start)
a(n) = A005252(n) - (-cos((2*n+1)*Pi/3)/2 - sqrt(3)*sin((2*n+1)*Pi/3)/6 + sqrt(3)*cos(Pi*n/3+Pi/6)/6 + sin((2*n+1)*Pi/6)/2).
a(n) = Sum_{k=0..floor(n/2)} if(mod(n-k, 2)=0, binomial(n-k, k), 0).
a(n) = A093040(n-1) - Fibonacci(n). (End)
a(n) = Sum_{k=0..floor(n/2)} C(n-k, k)*(1+(-1)^(n-k))/2. - Paul Barry, Sep 09 2005
From Paul Barry, Feb 04 2006: (Start)
a(n) = Sum_{k=0..floor(n/2)} C(2*k, n-2*k).
a(n) = Sum_{k=0..floor(n/2)} C(n-k,k)*C(3*k,n-k)/C(3*k,k). (End)
2*a(n) = A000045(n+1) + A049347(n). - R. J. Mathar, Feb 13 2020
a(n) = (1/2)*(A000045(n+1) + A049347(n)). - G. C. Greubel, Feb 09 2023

A073778 a(n) = Sum_{k=0..n} T(k)*T(n-k), where T is A000073; convolution of A000073 with itself.

Original entry on oeis.org

0, 0, 0, 0, 1, 2, 5, 12, 26, 56, 118, 244, 499, 1010, 2027, 4040, 8004, 15776, 30956, 60504, 117845, 228818, 443057, 855732, 1649022, 3171128, 6086626, 11662252, 22309543, 42614178, 81286743, 154856528, 294660040, 560052736, 1063367384, 2017030256
Offset: 0

Views

Author

Mario Catalani (mario.catalani(AT)unito.it), Aug 10 2002

Keywords

Comments

Number of binary sequences of length n+1 that have exactly one subsequence 000. Example: a(4)=5 because we have 00010,00011,01000,10001 and 11000. Column 1 of A118390. - Emeric Deutsch, Apr 27 2006
Let (b(n)) be the p-INVERT of (1,1,1,0,0,0,0,0,0,...) using p(S) = 1 - S^2; then b(n) = a(n+3) for n >= 0. See A292324. - Clark Kimberling, Sep 15 2017

Crossrefs

Programs

  • Maple
    A073778:=proc(n) coeftayl(x^4/(1-x-x^2-x^3)^2, x=0, n); end proc: seq(A073778(n), n=0..40); # Wesley Ivan Hurt, Nov 17 2014
  • Mathematica
    CoefficientList[Series[x^4/(1-x-x^2-x^3)^2, {x, 0, 40}], x]
  • Maxima
    a(n):= sum((k+1)*sum(binomial(j,n-3*k+2*j-4)*binomial(k,j), j,0,k), k,0,n-4);
    makelist(a(n), n, 0, 30); /* Vladimir Kruchinin, Dec 14 2011 */
    
  • PARI
    T(n) = ([0, 1, 0; 0, 0, 1; 1, 1, 1]^n)[1, 3]; \\ A000073
    a(n) = sum(k=0, n, T(k)*T(n-k)); \\ Michel Marcus, Oct 20 2021
  • Sage
    [( x^4/(1-x-x^2-x^3)^2 ).series(x,n+1).list()[n] for n in (0..40)] # Zerinvary Lajos, Jun 02 2009; modified by G. C. Greubel, Dec 15 2021
    

Formula

G.f.: x^4/(1 - x - x^2 - x^3)^2.
a(n) = Sum_{k=0..n-4} (k+1)*Sum_{j=0..k} binomial(j,n-3*k+2*j-4)*binomial(k,j). - Vladimir Kruchinin, Dec 14 2011
(n-2)*a(n) - (n-1)*a(n-1) - n*a(n-2) - (n+1)*a(n-3) = 0, n > 2. - Michael D. Weiner, Nov 18 2014

Extensions

Two initial zeros inserted by Hans J. H. Tuenter, Oct 20 2021

A292402 p-INVERT of (1,0,0,1,0,0,0,0,0,0,...), where p(S) = 1 - S^2.

Original entry on oeis.org

0, 1, 0, 1, 2, 1, 4, 2, 6, 7, 8, 16, 14, 29, 32, 47, 70, 82, 136, 162, 244, 331, 440, 650, 834, 1220, 1632, 2262, 3176, 4261, 6056, 8175, 11414, 15747, 21568, 30121, 41094, 57210, 78644, 108521, 150300, 206456, 286288, 393865, 544424, 751675, 1035980
Offset: 0

Views

Author

Clark Kimberling, Sep 30 2017

Keywords

Comments

Suppose s = (c(0), c(1), c(2), ...) is a sequence and p(S) is a polynomial. Let S(x) = c(0)*x + c(1)*x^2 + c(2)*x^3 + ... and T(x) = (-p(0) + 1/p(S(x)))/x. The p-INVERT of s is the sequence t(s) of coefficients in the Maclaurin series for T(x). Taking p(S) = 1 - S gives the "INVERT" transform of s, so that p-INVERT is a generalization of the "INVERT" transform (e.g., A033453).

Crossrefs

Programs

  • Mathematica
    z = 60; s = x + x^4; p = 1 - s^2;
    Drop[CoefficientList[Series[s, {x, 0, z}], x], 1]
    Drop[CoefficientList[Series[1/p, {x, 0, z}], x], 1]  (* A292402 *)

Formula

G.f.: -((x (1 + x)^2 (1 - x + x^2)^2)/((-1 + x + x^4) (1 + x + x^4))).
a(n) = a(n-2) + 2*a(n-5) + a(n-8) for n >= 9.

A099444 A Chebyshev transform of Fib(2n+2).

Original entry on oeis.org

1, 3, 7, 15, 32, 69, 149, 321, 691, 1488, 3205, 6903, 14867, 32019, 68960, 148521, 319873, 688917, 1483735, 3195552, 6882329, 14822619, 31923791, 68754951, 148079008, 318920925, 686866813, 1479319737, 3186042539, 6861847920
Offset: 0

Views

Author

Paul Barry, Oct 16 2004

Keywords

Comments

The denominator is a parameterization of the Alexander polynomial for the knot 6_2 (Miller Institute knot). The g.f. is the image of the g.f. of Fib(2n+2) under the Chebyshev transform A(x)->(1/(1+x^2))A(x/(1+x^2)).
This sequence is the p-INVERT of A010892 using p(S) = 1 - S - S^2; see A292324. - Clark Kimberling, Sep 26 2017

Crossrefs

Cf. A001906.

Programs

  • Mathematica
    LinearRecurrence[{3,-3,3,-1},{1,3,7,15},30] (* Harvey P. Dale, Sep 30 2018 *)

Formula

G.f.: (1+x^2)/(1-3x+3x^2-3x^3+x^4);
a(n) = sum{k=0..floor(n/2), binomial(n-k, k)(-1)^k*Fib(2(n-2k)+2)};
a(n) = sum{k=0..n, binomial((n+k)/2, k)(-1)^((n-k)/2)(1+(-1)^(n+k))Fib(2k+2)/2};
a(n) = sum{k=0..n, A099445(n-k)*binomial(1, k/2)(1+(-1)^k)/2}.

A292326 p-INVERT of (1,1,1,0,0,0,0,0,0,0,0,...), where p(S) = (1 - S)^3.

Original entry on oeis.org

3, 9, 25, 63, 153, 359, 819, 1830, 4018, 8694, 18582, 39298, 82350, 171186, 353338, 724719, 1478061, 2999175, 6057687, 12183945, 24411935, 48740193, 96998325, 192459996, 380812692, 751557756, 1479686972, 2906717460, 5698014924, 11147786740, 21769549380
Offset: 0

Views

Author

Clark Kimberling, Sep 15 2017

Keywords

Comments

Suppose s = (c(0), c(1), c(2), ...) is a sequence and p(S) is a polynomial. Let S(x) = c(0)*x + c(1)*x^2 + c(2)*x^3 + ... and T(x) = (-p(0) + 1/p(S(x)))/x. The p-INVERT of s is the sequence t(s) of coefficients in the Maclaurin series for T(x). Taking p(S) = 1 - S gives the "INVERT" transform of s, so that p-INVERT is a generalization of the "INVERT" transform (e.g., A033453).

Crossrefs

Cf. A292324.

Programs

  • Mathematica
    z = 60; s = x + x^2 + x^3; p = (1 - s)^3;
    Drop[CoefficientList[Series[s, {x, 0, z}], x], 1]
    Drop[CoefficientList[Series[1/p, {x, 0, z}], x], 1]  (* A292326 *)
    LinearRecurrence[{3,0,-2,-6,0,4,6,3,1},{3,9,25,63,153,359,819,1830,4018},40] (* Harvey P. Dale, Nov 01 2019 *)

Formula

G.f.: -(((1 + x + x^2) (3 - 3 x - 2 x^2 - x^3 + 3 x^4 + 2 x^5 + x^6))/(-1 + x + x^2 + x^3)^3).
a(n) = 3*a(n-1) - 2*a(n-3) - 6*a(n-4) + 4*a(n-6) + 6*a(n-7) + 3*a(n-8) + a(n-9) for n >= 10.

A292325 p-INVERT of (1,0,0,0,1,0,0,0,0,0,...), where p(S) = (1 - S)^2.

Original entry on oeis.org

2, 3, 4, 5, 8, 13, 20, 29, 40, 56, 80, 115, 164, 230, 320, 445, 620, 864, 1200, 1660, 2290, 3155, 4344, 5975, 8206, 11252, 15408, 21078, 28810, 39344, 53680, 73173, 99662, 135640, 184480, 250740, 340578, 462316, 627200, 850420, 1152480, 1561043, 2113420
Offset: 0

Views

Author

Clark Kimberling, Sep 15 2017

Keywords

Comments

Suppose s = (c(0), c(1), c(2), ...) is a sequence and p(S) is a polynomial. Let S(x) = c(0)*x + c(1)*x^2 + c(2)*x^3 + ... and T(x) = (-p(0) + 1/p(S(x)))/x. The p-INVERT of s is the sequence t(s) of coefficients in the Maclaurin series for T(x). Taking p(S) = 1 - S gives the "INVERT" transform of s, so that p-INVERT is a generalization of the "INVERT" transform (e.g., A033453).

Crossrefs

Programs

  • Mathematica
    z = 60; s = x + x^5; p = (1 - s)^2;
    Drop[CoefficientList[Series[s, {x, 0, z}], x], 1]
    Drop[CoefficientList[Series[1/p, {x, 0, z}], x], 1]  (* A292325 *)

Formula

G.f.: -(((-1 + x) (1 + x^4) (2 + x + x^2 + x^3 + x^4))/((1 - x + x^2)^2 (-1 + x^2 + x^3)^2)).
a(n) = 2*a(n-1) - a(n-2) + 2*a(n-5) - 2*a(n-6) - a(n-10) for n >= 11.

A259074 Triangle T(n,k) = Sum_{j=0..(n-k)/3} C(n-3*j-1,k-1)*C(n-k-3*j,j).

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 1, 3, 3, 1, 2, 4, 6, 4, 1, 3, 7, 10, 10, 5, 1, 4, 12, 18, 20, 15, 6, 1, 5, 19, 33, 39, 35, 21, 7, 1, 7, 28, 58, 76, 75, 56, 28, 8, 1, 10, 42, 96, 144, 156, 132, 84, 36, 9, 1, 14, 64, 156, 260, 315, 294, 217, 120, 45, 10, 1, 19, 97, 253, 455, 610, 630, 518, 338, 165, 55, 11, 1
Offset: 1

Views

Author

Vladimir Kruchinin, Jun 18 2015

Keywords

Examples

			[1]
[1,1]
[1,2,1]
[1,3,3,1]
[2,4,6,4,1]
[3,7,10,10,5,1]
		

Crossrefs

Column k=1 gives A003269, column k=2 A292324.
Row sums give A008999(n-1) for n>0.

Programs

  • Mathematica
    Table[Sum[Binomial[n - 3*j - 1, k - 1] Binomial[n - k - 3*j, j], {j, 0, (n - k)/3}], {n, 12}, {k, n}] // Flatten (* Michael De Vlieger, Jun 19 2015 *)
  • Maxima
    T(n,k):=sum(binomial(n-3*j-1,k-1)*binomial(n-k-3*j,j),j,0,(n-k)/3);

Formula

G.f.: (x*y)/(1-x-x^4-x*y).
Showing 1-7 of 7 results.