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 15 results. Next

A017907 Expansion of 1/(1 - x^13 - x^14 - ...).

Original entry on oeis.org

1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 19, 23, 28, 34, 41, 49, 58, 68, 79, 91, 104, 118, 134, 153, 176, 204, 238, 279, 328, 386, 454, 533, 624, 728, 846, 980, 1133, 1309
Offset: 0

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Author

Keywords

Comments

a(n) = number of compositions of n in which each part is >= 13. - Milan Janjic, Jun 28 2010
a(n+25) equals the number of binary words of length n having at least 12 zeros between every two successive ones. - Milan Janjic, Feb 09 2015

Crossrefs

Column k=12 of A141539, k=13 of A220122. - Alois P. Heinz, Dec 09 2012

Programs

  • Maple
    a:= n-> (Matrix(13, (i,j)-> if (i=j-1) then 1 elif j=1 then [1, 0$11, 1][i] else 0 fi)^n)[13,13]: seq(a(n), n=0..80); # Alois P. Heinz, Aug 04 2008
  • Mathematica
    LinearRecurrence[{1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1}, {1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, 80] (* Vladimir Joseph Stephan Orlovsky, Feb 17 2012 *)
    CoefficientList[Series[(x-1)/(x-1+x^13),{x,0,70}],x] (* Harvey P. Dale, Feb 07 2015 *)
  • PARI
    Vec((x-1)/(x-1+x^13)+O(x^99)) \\ Charles R Greathouse IV, Sep 26 2012

Formula

G.f.: (x-1)/(x-1+x^13). - Alois P. Heinz, Aug 04 2008
For positive integers n and k such that k <= n <= 13*k, and 12 divides n-k, define c(n,k) = binomial(k,(n-k)/12), and c(n,k) = 0, otherwise. Then, for n>=1, a(n+13) = sum(c(n,k), k=1..n). - Milan Janjic, Dec 09 2011
a(0)=1, a(1)=0, a(2)=0, a(3)=0, a(4)=0, a(5)=0, a(6)=0, a(7)=0, a(8)=0, a(9)=0, a(10)=0, a(11)=0, a(12)=0, a(n)=a(n-1)+a(n-13). - Harvey P. Dale, Feb 07 2015

A220123 Number of tilings of a 4 X n rectangle using integer-sided rectangular tiles of area 4.

Original entry on oeis.org

1, 1, 2, 3, 9, 16, 35, 65, 143, 281, 590, 1174, 2440, 4925, 10142, 20563, 42178, 85819, 175632, 357875, 731536, 1491966, 3047879, 6218844, 12699982, 25919176, 52922491, 108022099, 220541999, 450186874, 919074255, 1876149465, 3830134125, 7818778884, 15961716918
Offset: 0

Views

Author

Alois P. Heinz, Dec 05 2012

Keywords

Examples

			a(3) = 3, because there are 3 tilings of a 4 X 3 rectangle using integer-sided rectangular tiles of area 4:
._._._.   ._.___.   .___._.
| | | |   | |   |   |   | |
| | | |   | |___|   |___| |
| | | |   | |   |   |   | |
|_|_|_|   |_|___|   |___|_|
		

Crossrefs

Column k=4 of A220122. Cf. A005178.

Programs

  • Maple
    gf:= -(x-1)*(x+1)*(x^2+1)/(x^8-x^6+x^5-5*x^4-x^2-x+1):
    a:= n-> coeff(series(gf, x, n+1), x, n):
    seq(a(n), n=0..50);

Formula

G.f.: -(x-1)*(x+1)*(x^2+1) / (x^8 - x^6 + x^5 - 5*x^4 - x^2 - x + 1).
a(n) = a(n-1) + a(n-2) + 5*a(n-4) - a(n-5) + a(n-6) - a(n-8). - Caleb Wagner, Nov 06 2013
a(2*n+1) = Sum_{k=0..n} A005178(k+1)*a(2*n-2*k). - Shravan Haribalaraman, Aug 29 2022

A220124 Number of tilings of a 6 X n rectangle using integer-sided rectangular tiles of area 6.

Original entry on oeis.org

1, 1, 2, 4, 7, 13, 46, 88, 209, 473, 1002, 2120, 5197, 11085, 25384, 57234, 126959, 279883, 640387, 1412460, 3182794, 7138463, 15963680, 35593612, 80143244, 178644947, 400681480, 897313564, 2008904252, 4492651815, 10074017008, 22526314856, 50459193392
Offset: 0

Views

Author

Alois P. Heinz, Dec 05 2012

Keywords

Examples

			a(4) = 7, because there are 7 tilings of a 6 X 4 rectangle using integer-sided rectangular tiles of area 6:
._._._._. ._._._._. ._._._._. ._._._._. ._._._._. ._._._._. ._._._._.
| | | | | |   | | | | |   | | | | |   | |   |   | |     | | | |     |
| | | | | |   | | | | |   | | | | |   | |   |   | |     | | | |     |
| | | | | |___| | | | |___| | | | |___| |___|___| |_____| | | |_____|
| | | | | |   | | | | |   | | | | |   | |   |   | |     | | | |     |
| | | | | |   | | | | |   | | | | |   | |   |   | |     | | | |     |
|_|_|_|_| |___|_|_| |_|___|_| |_|_|___| |___|___| |_____|_| |_|_____|
		

Crossrefs

Column k=6 of A220122.

A220125 Number of tilings of an 8 X n rectangle using integer-sided rectangular tiles of area 8.

Original entry on oeis.org

1, 1, 2, 3, 9, 16, 35, 65, 250, 495, 1209, 2412, 6510, 13707, 32467, 68285, 176843, 387518, 926118, 2022259, 4928293, 11009067, 25938745, 57797488, 137808762, 311753120, 730878789, 1651849769, 3880235364, 8842052707, 20602970440, 46930887843, 109406749213
Offset: 0

Views

Author

Alois P. Heinz, Dec 06 2012

Keywords

Examples

			a(3) = 3, because there are 3 tilings of an 8 X 3 rectangle using integer-sided rectangular tiles of area 8:
._._._.   .___._.   ._.___.
| | | |   |   | |   | |   |
| | | |   |   | |   | |   |
| | | |   |   | |   | |   |
| | | |   |___| |   | |___|
| | | |   |   | |   | |   |
| | | |   |   | |   | |   |
| | | |   |   | |   | |   |
|_|_|_|   |___|_|   |_|___|
		

Crossrefs

Column k=8 of A220122.

A220126 Number of tilings of a 9 X n rectangle using integer-sided rectangular tiles of area 9.

Original entry on oeis.org

1, 1, 1, 2, 3, 4, 6, 9, 13, 37, 64, 95, 188, 326, 513, 875, 1449, 2302, 4289, 7422, 12072, 21561, 37559, 62571, 107806, 184027, 306628, 532661, 915705, 1537768, 2654311, 4574383, 7752577, 13292546, 22778306, 38625110, 66213867, 113475693, 192821642, 330086669
Offset: 0

Views

Author

Alois P. Heinz, Dec 06 2012

Keywords

Examples

			a(5) = 4, because there are 4 tilings of a 9 X 5 rectangle using integer-sided rectangular tiles of area 9:
._._._._._.  ._____._._.  ._._____._.  ._._._____.
| | | | | |  |     | | |  | |     | |  | | |     |
| | | | | |  |     | | |  | |     | |  | | |     |
| | | | | |  |_____| | |  | |_____| |  | | |_____|
| | | | | |  |     | | |  | |     | |  | | |     |
| | | | | |  |     | | |  | |     | |  | | |     |
| | | | | |  |_____| | |  | |_____| |  | | |_____|
| | | | | |  |     | | |  | |     | |  | | |     |
| | | | | |  |     | | |  | |     | |  | | |     |
|_|_|_|_|_|  |_____|_|_|  |_|_____|_|  |_|_|_____|
		

Crossrefs

Column k=9 of A220122.

A220127 Number of tilings of a 10 X n rectangle using integer-sided rectangular tiles of area 10.

Original entry on oeis.org

1, 1, 2, 3, 5, 9, 15, 26, 44, 75, 254, 470, 1130, 2150, 4369, 8889, 17112, 33235, 62619, 117687, 259213, 500978, 1073742, 2114851, 4334588, 8817832, 17673956, 35420952, 69871967, 137274169, 281650158, 556043329, 1139084899, 2264971273, 4589226181, 9256382600
Offset: 0

Views

Author

Alois P. Heinz, Dec 06 2012

Keywords

Examples

			a(4) = 5, because there are 5 tilings of a 10 X 4 rectangle using integer-sided rectangular tiles of area 10:
._._._._.   .___._._.   ._.___._.   ._._.___.   .___.___.
| | | | |   |   | | |   | |   | |   | | |   |   |   |   |
| | | | |   |   | | |   | |   | |   | | |   |   |   |   |
| | | | |   |   | | |   | |   | |   | | |   |   |   |   |
| | | | |   |   | | |   | |   | |   | | |   |   |   |   |
| | | | |   |___| | |   | |___| |   | | |___|   |___|___|
| | | | |   |   | | |   | |   | |   | | |   |   |   |   |
| | | | |   |   | | |   | |   | |   | | |   |   |   |   |
| | | | |   |   | | |   | |   | |   | | |   |   |   |   |
| | | | |   |   | | |   | |   | |   | | |   |   |   |   |
|_|_|_|_|   |___|_|_|   |_|___|_|   |_|_|___|   |___|___|
		

Crossrefs

Column k=10 of A220122.

A220128 1 followed by period 6: (1, 3, 2, 3, 1, 4) repeated; offset 0.

Original entry on oeis.org

1, 1, 3, 2, 3, 1, 4, 1, 3, 2, 3, 1, 4, 1, 3, 2, 3, 1, 4, 1, 3, 2, 3, 1, 4, 1, 3, 2, 3, 1, 4, 1, 3, 2, 3, 1, 4, 1, 3, 2, 3, 1, 4, 1, 3, 2, 3, 1, 4, 1, 3, 2, 3, 1, 4, 1, 3, 2, 3, 1, 4, 1, 3, 2, 3, 1, 4, 1, 3, 2, 3, 1, 4, 1, 3, 2, 3, 1, 4, 1, 3, 2, 3, 1, 4, 1, 3
Offset: 0

Views

Author

Alois P. Heinz, Dec 06 2012

Keywords

Comments

Also the number of tilings of an n X 3 rectangle using integer-sided rectangular tiles of area n.
Also decimal expansion of 12443/109890 = 0.1132314132314... .

Examples

			a(6) = 4, because there are 4 tilings of a 6 X 3 rectangle using integer-sided rectangular tiles of area 6:
._._._.  .___._.  ._.___.  ._____.
| | | |  |   | |  | |   |  |     |
| | | |  |   | |  | |   |  |_____|
| | | |  |___| |  | |___|  |     |
| | | |  |   | |  | |   |  |_____|
| | | |  |   | |  | |   |  |     |
|_|_|_|  |___|_|  |_|___|  |_____|
		

Crossrefs

Row n=3 of A220122.

Programs

  • Magma
    [1] cat &cat [[1, 3, 2, 3, 1, 4]^^20]; // Wesley Ivan Hurt, Jun 20 2016
  • Maple
    a:=n-> `if`(n=0, 1, [4, 1, 3, 2, 3, 1][irem(n, 6)+1]): seq(a(n), n=0..100);
  • Mathematica
    PadRight[{1}, 120, {4,1,3,2,3,1}] (* Harvey P. Dale, Jan 06 2016 *)

Formula

G.f.: (-3*x^4-4*x^3-4*x^2-2*x-1) / (x^4+x^3-x-1).
From Wesley Ivan Hurt, Jun 20 2016: (Start)
a(n) + a(n-1) = a(n-3) + a(n-4) for n>4.
a(0) = 1, a(n) = (7 + 3*cos(n*Pi) + 2*cos(2*n*Pi/3))/3 for n>0. (End)
E.g.f.: 2*(-9/2 + cos(sqrt(3)*x/2)*exp(-x/2) + 2*sinh(x) + 5*cosh(x))/3. - Ilya Gutkovskiy, Jun 21 2016

A220129 1 followed by period 12: (1, 5, 3, 9, 1, 7, 1, 9, 3, 5, 1, 11) repeated; offset 0.

Original entry on oeis.org

1, 1, 5, 3, 9, 1, 7, 1, 9, 3, 5, 1, 11, 1, 5, 3, 9, 1, 7, 1, 9, 3, 5, 1, 11, 1, 5, 3, 9, 1, 7, 1, 9, 3, 5, 1, 11, 1, 5, 3, 9, 1, 7, 1, 9, 3, 5, 1, 11, 1, 5, 3, 9, 1, 7, 1, 9, 3, 5, 1, 11, 1, 5, 3, 9, 1, 7, 1, 9, 3, 5, 1, 11, 1, 5, 3, 9, 1, 7, 1, 9, 3, 5, 1, 11
Offset: 0

Views

Author

Alois P. Heinz, Dec 06 2012

Keywords

Comments

Also the number of tilings of an n X 4 rectangle using integer-sided rectangular tiles of area n.

Examples

			a(6) = 7, because there are 7 tilings of a 6 X 4 rectangle using integer-sided rectangular tiles of area 6:
._._._._.  ._._._._.  ._._____.  .___._._.
| | | | |  |     | |  | |     |  |   | | |
| | | | |  |_____| |  | |_____|  |   | | |
| | | | |  |     | |  | |     |  |___| | |
| | | | |  |_____| |  | |_____|  |   | | |
| | | | |  |     | |  | |     |  |   | | |
|_|_|_|_|  |_____|_|  |_|_____|  |___|_|_|
._.___._.  ._._.___.  .___.___.
| |   | |  | | |   |  |   |   |
| |   | |  | | |   |  |   |   |
| |___| |  | | |___|  |___|___|
| |   | |  | | |   |  |   |   |
| |   | |  | | |   |  |   |   |
|_|___|_|  |_|_|___|  |___|___|
		

Crossrefs

Row n=4 of A220122.

Programs

  • Maple
    a:= n-> `if`(n=0, 1, [11, 1, 5, 3, 9, 1, 7, 1, 9, 3, 5, 1][irem(n, 12)+1]):
    seq(a(n), n=0..100);
  • Mathematica
    PadRight[{1},120,{11,1,5,3,9,1,7,1,9,3,5,1}] (* Harvey P. Dale, Aug 24 2025 *)

Formula

G.f.: -(10*x^6+11*x^5+16*x^4+9*x^3+7*x^2+2*x+1) / (x^6+x^5+x^4-x^2-x-1).

A220130 Number of tilings of an n X 5 rectangle using integer-sided rectangular tiles of area n.

Original entry on oeis.org

1, 1, 8, 4, 16, 2, 13, 1, 16, 4, 9, 1, 21, 1, 8, 5, 16, 1, 13, 1, 17, 4, 8, 1, 21, 2, 8, 4, 16, 1, 14, 1, 16, 4, 8, 2, 21, 1, 8, 4, 17, 1, 13, 1, 16, 5, 8, 1, 21, 1, 9, 4, 16, 1, 13, 2, 16, 4, 8, 1, 22, 1, 8, 4, 16, 2, 13, 1, 16, 4, 9, 1, 21, 1, 8, 5, 16, 1
Offset: 0

Views

Author

Alois P. Heinz, Dec 06 2012

Keywords

Comments

1 followed by period 60: (1, 8, ..., 22) repeated; offset 0.

Examples

			a(3) = 4, because there are 4 tilings of a 3 X 5 rectangle using integer-sided rectangular tiles of area 3:
._._._._._.   ._____._._.   ._._____._.   ._._._____.
| | | | | |   |_____| | |   | |_____| |   | | |_____|
| | | | | |   |_____| | |   | |_____| |   | | |_____|
|_|_|_|_|_|   |_____|_|_|   |_|_____|_|   |_|_|_____|
		

Crossrefs

Row n=5 of A220122.

Programs

  • Maple
    gf:= -(21*x^12 +22*x^11 +51*x^10 +56*x^9 +80*x^8 +65*x^7 +72*x^6 +45*x^5 +40*x^4 +16*x^3 +11*x^2 +2*x +1) / (x^12 +x^11 +2*x^10 +2*x^9 +2*x^8 +x^7 -x^5 -2*x^4 -2*x^3 -2*x^2 -x -1):
    a:= n-> coeff(series(gf, x, n+1), x, n):
    seq(a(n), n=0..100);

Formula

G.f.: see Maple program.

A220131 Number of tilings of an n X 6 rectangle using integer-sided rectangular tiles of area n.

Original entry on oeis.org

1, 1, 13, 6, 35, 3, 46, 1, 35, 6, 15, 1, 88, 1, 13, 8, 35, 1, 46, 1, 37, 6, 13, 1, 88, 3, 13, 6, 35, 1, 48, 1, 35, 6, 13, 3, 88, 1, 13, 6, 37, 1, 46, 1, 35, 8, 13, 1, 88, 1, 15, 6, 35, 1, 46, 3, 35, 6, 13, 1, 90, 1, 13, 6, 35, 3, 46, 1, 35, 6, 15, 1, 88, 1, 13
Offset: 0

Views

Author

Alois P. Heinz, Dec 06 2012

Keywords

Comments

1 followed by period 60: (1, 13, ..., 90) repeated; offset 0.

Examples

			a(3) = 6, because there are 6 tilings of a 3 X 6 rectangle using integer-sided rectangular tiles of area 3:
._._._._._._.   ._____._._._.   ._._____._._.
| | | | | | |   |_____| | | |   | |_____| | |
| | | | | | |   |_____| | | |   | |_____| | |
|_|_|_|_|_|_|   |_____|_|_|_|   |_|_____|_|_|
._._._____._.   ._._._._____.   ._____._____.
| | |_____| |   | | | |_____|   |_____|_____|
| | |_____| |   | | | |_____|   |_____|_____|
|_|_|_____|_|   |_|_|_|_____|   |_____|_____|
		

Crossrefs

Row n=6 of A220122.

Programs

  • Maple
    gf:= -(89*x^16 +90*x^15 +103*x^14 +109*x^13 +144*x^12 +58*x^11 +103*x^10 +91*x^9 +120*x^8 +91*x^7 +103*x^6 +58*x^5 +56*x^4 +21*x^3 +15*x^2 +2*x +1) / (x^16 +x^15 +x^14 +x^13 +x^12 -x^4 -x^3 -x^2 -x -1):
    a:= n-> coeff(series(gf, x, n+1), x, n):
    seq(a(n), n=0..100);

Formula

G.f.: see Maple program.
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