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

A159288 Expansion of (1 + x + x^2)/(1 - x^2 - 2*x^3).

Original entry on oeis.org

1, 1, 2, 3, 4, 7, 10, 15, 24, 35, 54, 83, 124, 191, 290, 439, 672, 1019, 1550, 2363, 3588, 5463, 8314, 12639, 19240, 29267, 44518, 67747, 103052, 156783, 238546, 362887, 552112, 839979, 1277886, 1944203, 2957844, 4499975, 6846250, 10415663
Offset: 0

Views

Author

Creighton Dement, Apr 08 2009

Keywords

Comments

A floretion-generated sequence: 'i + 0.5('ij' + 'ik' + 'ji' + 'jk' + 'ki' + 'kj')
Starting with offset 1 the sequence appears to be the INVERT transform of (1, 1, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0, ...). - Gary W. Adamson, Aug 27 2016

Crossrefs

Programs

  • Magma
    I:=[1, 1, 2]; [n le 3 select I[n] else Self(n-2) + 2*Self(n-2): n in [1..30]]; // G. C. Greubel, Jun 27 2018
  • Mathematica
    CoefficientList[Series[(1+x+x^2)/(1-x^2-2x^3),{x,0,50}],x]  (* Harvey P. Dale, Mar 09 2011 *)
    LinearRecurrence[{0, 1, 2}, {1, 1, 2}, 50] (* G. C. Greubel, Jun 27 2018 *)
  • PARI
    a(n)=([0,1,0; 0,0,1; 2,1,0]^n*[1;1;2])[1,1] \\ Charles R Greathouse IV, Aug 27 2016
    
  • PARI
    Vec((1 + x + x^2) / (1 - x^2 - 2*x^3) + O(x^40)) \\ Colin Barker, Apr 29 2019
    

Formula

a(n) = A159287(n) + A159287(n+1) + A159287(n+2). - R. J. Mathar, Apr 10 2009
a(n) = a(n-2) + 2*a(n-3) for n>2. - Colin Barker, Apr 29 2019
a(n)= A052947(n) + A052947(n-1) +A052947(n-2). - R. J. Mathar, Mar 23 2023

A159287 Expansion of x^2/(1-x^2-2*x^3).

Original entry on oeis.org

0, 0, 1, 0, 1, 2, 1, 4, 5, 6, 13, 16, 25, 42, 57, 92, 141, 206, 325, 488, 737, 1138, 1713, 2612, 3989, 6038, 9213, 14016, 21289, 32442, 49321, 75020, 114205, 173662, 264245, 402072, 611569, 930562, 1415713, 2153700, 3276837, 4985126, 7584237, 11538800
Offset: 0

Views

Author

Creighton Dement, Apr 08 2009

Keywords

Comments

A floretion-generated sequence: 'i + 0.5('ij' + 'ik' + 'ji' + 'jk' + 'ki' + 'kj').
From Greg Dresden, Nov 15 2024: (Start)
a(n) is the number of ways to tile a 2 X (n+1) board with L-shaped trominos and S-shaped quadrominos, where the first tile must be an upright L. For example, here are the a(7)=4 ways to tile a 2 X 8 board:
| | | | | | | | | | | |
|_|_||__|___| |_|___|||___|
| | | | | | | | | | | |
|_|_|_|___|| |__|___||__|_| (End)

Crossrefs

Essentially the same as A052947.

Programs

Formula

G.f.: x^2/(1-x^2-2*x^3).
a(n) = A052947(n-2). - R. J. Mathar, Nov 10 2009
a(n) = a(n-2) + 2*a(n-3). - Wesley Ivan Hurt, May 23 2023
From Greg Dresden, Nov 17 2024: (Start)
a(2*n+1) = 2*a(n)^2 + 2*a(n+1)*a(n+2).
a(3*n+1) = Sum_{i=1..n} a(3*i-2)*2^(n-i). (End)

A107852 Expansion of -x*(x^2+1)*(x+1)^2/((2*x^3+x^2-1)*(x^4+1)).

Original entry on oeis.org

0, 1, 2, 3, 6, 7, 10, 17, 22, 37, 58, 83, 134, 199, 298, 465, 694, 1061, 1626, 2451, 3750, 5703, 8650, 13201, 20054, 30501, 46458, 70611, 107462, 163527, 248682, 378449, 575734, 875813, 1332634, 2027283, 3084262, 4692551, 7138826, 10861073
Offset: 0

Views

Author

Creighton Dement, May 25 2005

Keywords

Comments

Floretion Algebra Multiplication Program, FAMP Code: 1baseiforzapseq[(.5i' + .5j' + .5'ki' + .5'kj')*(.5'i + .5'j + .5'ik' + .5'jk')], 1vesforzap = A000004

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[-x(x^2+1)(x+1)^2/((2x^3+x^2-1)(x^4+1)),{x,0, 50}],x] (* or *) LinearRecurrence[ {0,1,2,-1,0,1,2},{0,1,2,3,6,7,10},50] (* Harvey P. Dale, May 03 2024 *)
  • PARI
    a(n)=([0,1,0,0,0,0,0; 0,0,1,0,0,0,0; 0,0,0,1,0,0,0; 0,0,0,0,1,0,0; 0,0,0,0,0,1,0; 0,0,0,0,0,0,1; 2,1,0,-1,2,1,0]^n*[0;1;2;3;6;7;10])[1,1] \\ Charles R Greathouse IV, Oct 03 2016
    
  • PARI
    concat(0, Vec(x*(1 + x)^2*(1 + x^2) / ((1 - x^2 - 2*x^3)*(1 + x^4)) + O(x^45))) \\ Colin Barker, Apr 30 2019

Formula

a(n) = 2*A159284(n) - A091337(n).
a(n) = a(n-2) + 2*a(n-3) - a(n-4) + a(n-6) + 2*a(n-7) for n>6. - Colin Barker, Apr 30 2019

A107851 Expansion of g.f. x*(-1-x-3*x^2-x^3+2*x^5)/((2*x^3+x^2-1)*(x^4+1)).

Original entry on oeis.org

0, 1, 1, 4, 4, 5, 9, 10, 18, 29, 41, 68, 100, 149, 233, 346, 530, 813, 1225, 1876, 2852, 4325, 6601, 10026, 15250, 23229, 35305, 53732, 81764, 124341, 189225, 287866, 437906, 666317, 1013641, 1542132, 2346276, 3569413, 5430537, 8261962, 12569362
Offset: 0

Views

Author

Creighton Dement, May 25 2005

Keywords

Comments

Floretion Algebra Multiplication Program, FAMP Code: 1jesforzapseq[(.5i' + .5j' + .5'ki' + .5'kj')*(.5'i + .5'j + .5'ik' + .5'jk')], 1vesforzap = A000004

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[x(-1-x-3x^2-x^3+2x^5)/((2x^3+x^2-1)(x^4+1)), {x,0,50}],x] (* or *) LinearRecurrence[{0,1,2,-1,0,1,2},{0,1,1,4,4,5,9},51] (* Harvey P. Dale, Jul 19 2011 *)
  • PARI
    a(n)=([0,1,0,0,0,0,0; 0,0,1,0,0,0,0; 0,0,0,1,0,0,0; 0,0,0,0,1,0,0; 0,0,0,0,0,1,0; 0,0,0,0,0,0,1; 2,1,0,-1,2,1,0]^n*[0;1;1;4;4;5;9])[1,1] \\ Charles R Greathouse IV, Oct 03 2016

Formula

a(n) = A159284(n+1) + A132380(n+7).
a(0)=0, a(1)=1, a(2)=1, a(3)=4, a(4)=4, a(5)=5, a(6)=9, a(n)= a(n-2)+ 2*a(n-3)-a(n-4)+a(n-6)+2*a(n-7). - Harvey P. Dale, Jul 19 2011

A159285 Expansion of (1+3*x)/(1-x^2-2*x^3).

Original entry on oeis.org

1, 3, 1, 5, 7, 7, 17, 21, 31, 55, 73, 117, 183, 263, 417, 629, 943, 1463, 2201, 3349, 5127, 7751, 11825, 18005, 27327, 41655, 63337, 96309, 146647, 222983, 339265, 516277, 785231, 1194807, 1817785, 2765269, 4207399, 6400839, 9737937, 14815637
Offset: 0

Views

Author

Creighton Dement, Apr 08 2009

Keywords

Comments

A floretion-generated sequence: 'i + 0.5('ij' + 'ik' + 'ji' + 'jk' + 'ki' + 'kj')

Crossrefs

Programs

  • Magma
    I:=[1,3,1]; [n le 3 select I[n] else Self(n-2) + 2*Self(n-3): n in [1..30]]; // G. C. Greubel, Jun 27 2018
  • Mathematica
    LinearRecurrence[{0, 1, 2}, {1, 3, 1}, 50] (* G. C. Greubel, Jun 27 2018 *)
    CoefficientList[Series[(1+3x)/(1-x^2-2x^3),{x,0,40}],x] (* Harvey P. Dale, Jan 21 2019 *)
  • PARI
    a(n)=([0,1,0; 0,0,1; 2,1,0]^n*[1;3;1])[1,1] \\ Charles R Greathouse IV, Oct 03 2016
    

Formula

a(n) = A052947(n) + 3*A052947(n-1). - R. J. Mathar, Mar 23 2023

A159286 Expansion of (x-1)^2/(1-x^2-2*x^3).

Original entry on oeis.org

1, -2, 2, 0, -2, 4, -2, 0, 6, -4, 6, 8, -2, 20, 14, 16, 54, 44, 86, 152, 174, 324, 478, 672, 1126, 1628, 2470, 3880, 5726, 8820, 13486, 20272, 31126, 47244, 71670, 109496, 166158, 252836, 385150, 585152
Offset: 0

Views

Author

Creighton Dement, Apr 08 2009

Keywords

Comments

A floretion-generated sequence: 'i + 0.5('ij' + 'ik' + 'ji' + 'jk' + 'ki' + 'kj').

Crossrefs

Programs

  • Magma
    I:=[1, -2, 2]; [n le 3 select I[n] else Self(n-2) + 2*Self(n-3): n in [1..30]]; // G. C. Greubel, Jun 27 2018
  • Mathematica
    CoefficientList[Series[(x-1)^2/(1-x^2-2*x^3),{x,0,40}],x] (* or *) LinearRecurrence[{0,1,2},{1,-2,2},40]  (* Harvey P. Dale, Apr 24 2011 *)
  • PARI
    a(n)=([0,1,0; 0,0,1; 2,1,0]^n*[1;-2;2])[1,1] \\ Charles R Greathouse IV, Oct 03 2016
    

Formula

a(n) = A159288(n) - 3*A159287(n+1). - R. J. Mathar, Apr 10 2009
a(1)=1, a(2)=-2, a(3)=2, a(n) = 1*a(n-2) + 2*a(n-3) for n >= 3. - Harvey P. Dale, Apr 24 2011
a(n) = A078026(n)-A078026(n-1). - R. J. Mathar, Mar 23 2023

A198295 Riordan array (1, x*(1+x)/(1-x^3)).

Original entry on oeis.org

1, 0, 1, 0, 1, 1, 0, 0, 2, 1, 0, 1, 1, 3, 1, 0, 1, 2, 3, 4, 1, 0, 0, 4, 4, 6, 5, 1, 0, 1, 2, 9, 8, 10, 6, 1, 0, 1, 3, 9, 17, 15, 15, 7, 1, 0, 0, 6, 9, 24, 30, 26, 21, 8, 1, 0, 1, 3, 18, 26, 51, 51, 42, 28, 9, 1
Offset: 0

Views

Author

Philippe Deléham, Jan 26 2012

Keywords

Comments

Triangle T(n,k), read by rows, given by (0, 1, -1, -1, 2, -1, 0, 0, 0, 0, 0, 0, 0, ...) DELTA (1, 0, 0, 0, 0, 0, 0, 0, ...) where DELTA is the operator defined in A084938.
Antidiagonals sums: see A159284.

Examples

			Triangle begins:
1
0, 1
0, 1, 1
0, 0, 2, 1
0, 1, 1, 3, 1
0, 1, 2, 3, 4, 1
0, 0, 4, 4, 6, 5, 1
0, 1, 2, 9, 8, 10, 6, 1
0, 1, 3, 9, 17, 15, 15, 7, 1
		

References

  • A. Luzón, D. Merlini, M. A. Morón, R. Sprugnoli, Complementary Riordan arrays, Discrete Applied Mathematics, 172 (2014) 75-87.

Crossrefs

Cf. Diagonals: A000012, A001477, A161680, A000125.

Formula

Sum_{k, 0<=k<=n} T(n,k) = A001590(n+2), n>0.
Sum_{k, 0<=k<=n}T(n,k)*(-1)^(n-k) = A078056(n-1), n>0.
T(n,n) = A000012(n), T(n+1,n) = A001477(n) = n, T(n+2,n) = A161680(n) = A000217(n-1); T(n+3,n) = A000125(n-1), n>=1.
G.f.: (-1+x)*(1+x+x^2)/(-1+x^3+x*y+x^2*y). - R. J. Mathar, Aug 11 2015

A237714 Expansion of (1 + x)/(1 - x^2 - 2*x^5).

Original entry on oeis.org

1, 1, 1, 1, 1, 3, 3, 5, 5, 7, 11, 13, 21, 23, 35, 45, 61, 87, 107, 157, 197, 279, 371, 493, 685, 887, 1243, 1629, 2229, 2999, 4003, 5485, 7261, 9943, 13259, 17949, 24229, 32471, 44115, 58989, 80013, 107447, 144955, 195677, 262933, 355703, 477827, 645613, 869181, 1171479, 1580587
Offset: 0

Views

Author

Sergio Falcon, Feb 12 2014

Keywords

Crossrefs

Programs

  • Mathematica
    For[j = 0, j < 5, j++, a[j] = 1]
    For[j = 5, j < 51, j++, a[j] = 2 a[j - 5] + a[j - 2]]
    Table[a[j], {j, 0, 50}]
    CoefficientList[Series[(1 + x)/(1 - x^2 - 2 x^5), {x, 0, 40}], x] (* Vincenzo Librandi, Feb 26 2014 *)
    LinearRecurrence[{0,1,0,0,2},{1,1,1,1,1},70] (* Harvey P. Dale, Nov 24 2024 *)
  • PARI
    Vec( (1 + x)/(1 - x^2 - 2*x^5) + O(x^66) ) \\ Joerg Arndt, Feb 24 2014

Formula

a(0)=1, a(1)=1, a(2)=1, a(3)=1, a(4)=1, a(n) = 2*a(n-5) + a(n-2) for n>=5.
a(2n) = sum_{j=0}^{n/5}C(n-3j,2j)*2^(2j)+sum_{j=0}^{(n-3)/5} C(n-2-3j,2j+1)*2^(2j+1).
a(2n+1) = sum_{j=0}^{n/5}C(n-3j,2j)*2^(2j)+sum_{j=0}^{(n-2)/5} C(n-1-3j,2j+1)*2^(2j+1).

A172358 Triangle read by rows: T(n,k) = round(c(n)/(c(k)*c(n-k))) where c are partial products of a sequence defined in comments.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 3, 3, 1, 1, 3, 9, 9, 3, 1, 1, 5, 15, 45, 15, 5, 1, 1, 9, 45, 135, 135, 45, 9, 1, 1, 11, 99, 495, 495, 495, 99, 11, 1, 1, 19, 209, 1881, 3135, 3135, 1881, 209, 19, 1, 1, 29, 551, 6061, 18183, 30305, 18183, 6061, 551, 29, 1
Offset: 0

Views

Author

Roger L. Bagula, Feb 01 2010

Keywords

Comments

Start from the sequence A159284 and its partial products c(n) = 1, 1, 1, 1, 3, 9, 45, 405, 4455, 84645, 2454705, ... . Then T(n,k) = round( c(n)/(c(k)*c(n-k)) ).

Examples

			Triangle begins as:
  1;
  1,  1;
  1,  1,   1;
  1,  1,   1,    1;
  1,  3,   3,    3,     1;
  1,  3,   9,    9,     3,     1;
  1,  5,  15,   45,    15,     5,     1;
  1,  9,  45,  135,   135,    45,     9,    1;
  1, 11,  99,  495,   495,   495,    99,   11,   1;
  1, 19, 209, 1881,  3135,  3135,  1881,  209,  19,  1;
  1, 29, 551, 6061, 18183, 30305, 18183, 6061, 551, 29, 1;
		

Crossrefs

Cf. A172353 (q=1), this sequence (q=2), A172359 (q=4), A172360 (q=5).

Programs

  • Mathematica
    f[n_, q_]:= f[n, q]= If[n<3, Fibonacci[n], f[n-2, q] + q*f[n-3, q]];
    c[n_, q_]:= Product[f[j, q], {j,n}];
    T[n_, k_, q_]:= Round[c[n, q]/(c[k, q]*c[n-k, q])];
    Table[T[n, k, 2], {n,0,12}, {k,0,n}]//Flatten (* modified by G. C. Greubel, May 09 2021 *)
  • Sage
    @CachedFunction
    def f(n,q): return fibonacci(n) if (n<3) else f(n-2, q) + q*f(n-3, q)
    def c(n,q): return product( f(j,q) for j in (1..n) )
    def T(n,k,q): return round(c(n, q)/(c(k, q)*c(n-k, q)))
    flatten([[T(n,k,2) for k in (0..n)] for n in (0..12)]) # G. C. Greubel, May 09 2021

Formula

T(n, k, q) = round(c(n,q)/(c(k,q)*c(n-k,q))), where c(n,q) = Product_{j=1..n} f(j,q), f(n, q) = f(n-2, q) + q*f(n-3, q), f(0,q) = 0, f(1,q) = f(2,q) = 1, and q = 2. - G. C. Greubel, May 09 2021

Extensions

Definition corrected to give integral terms by G. C. Greubel, May 09 2021

A237716 7-distance Pell sequence.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 3, 3, 5, 5, 7, 7, 9, 13, 15, 23, 25, 37, 39, 55, 65, 85, 111, 135, 185, 213, 295, 343, 465, 565, 735, 935, 1161, 1525, 1847, 2455, 2977, 3925, 4847, 6247, 7897, 9941, 12807, 15895, 20657, 25589, 33151, 41383, 53033, 66997
Offset: 0

Views

Author

Sergio Falcon, Feb 12 2014

Keywords

Examples

			a(7)=2a(0)+a(5)=3; a(8)=2a(1)+a(6)=3; a(9)=2a(2)+a(7)=5.
		

Crossrefs

Programs

  • Mathematica
    For[j = 0, j < 7, j++, a[j] = 1]
    For[j = 7, j < 51, j++, a[j] = 2 a[j - 7] + a[j - 2]]
    Table[a[j], {j, 0, 50}]
    CoefficientList[Series[(1 + x)/(1 - x^2 - 2 x^7), {x,0,50}], x] (* G. C. Greubel, May 01 2017 *)
  • PARI
    Vec((1+x)/(1-x^2-2*x^7)+O(x^99)) \\ Charles R Greathouse IV, Mar 06 2014

Formula

a(0)=1, a(1)=1, a(2)=1, a(3)=1, a(4)=1, a(5)=1, a(6)=1; a(n) = 2*a(n-7) + a(n-2) for n>=7.
G.f.: (1 + x)/(1 - x^2 - 2*x^7).
a(2*n) = Sum_{j=0..n/7} binomial(n-5*j, 2*j)*2^(2*j) + Sum_{j=0..(n-4)/7} binomial(n-3-5*j, 2*j+1)*2^(2*j+1).
a(2*n+1) = Sum_{j=0..n/7} binomial(n-5*j, 2*j)*2^(2*j) + Sum_{j=0..(n-3)/7} binomial(n-2-5*j, 2*j+1)*2^(2*j+1).
Showing 1-10 of 14 results. Next