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.

Previous Showing 11-19 of 19 results.

A157728 a(n) = Fibonacci(n) - 4.

Original entry on oeis.org

1, 4, 9, 17, 30, 51, 85, 140, 229, 373, 606, 983, 1593, 2580, 4177, 6761, 10942, 17707, 28653, 46364, 75021, 121389, 196414, 317807, 514225, 832036, 1346265, 2178305, 3524574, 5702883, 9227461, 14930348, 24157813, 39088165, 63245982, 102334151
Offset: 5

Views

Author

N. J. A. Sloane, Jun 26 2010

Keywords

Comments

Partial sums of A071679. - R. J. Mathar, Oct 12 2010

Crossrefs

Programs

Formula

From R. J. Mathar, Oct 12 2010: (Start)
a(n) = 2*a(n-1) - a(n-3).
G.f.: x^5*(1+x)^2/((x-1)*(x^2+x-1)). (End)

A157729 a(n) = Fibonacci(n) + 5.

Original entry on oeis.org

5, 6, 6, 7, 8, 10, 13, 18, 26, 39, 60, 94, 149, 238, 382, 615, 992, 1602, 2589, 4186, 6770, 10951, 17716, 28662, 46373, 75030, 121398, 196423, 317816, 514234, 832045, 1346274, 2178314, 3524583, 5702892, 9227470, 14930357, 24157822, 39088174, 63245991, 102334160
Offset: 0

Views

Author

N. J. A. Sloane, Jun 26 2010

Keywords

Crossrefs

Programs

  • Haskell
    a157729 = (+ 5) . a000045
    a157729_list = 5 : 6 : map (subtract 5)
                           (zipWith (+) a157729_list $ tail a157729_list)
    -- Reinhard Zumkeller, Jul 30 2013
  • Magma
    [ Fibonacci(n) + 5: n in [0..40] ]; // Vincenzo Librandi, Apr 24 2011
    
  • Mathematica
    Fibonacci[Range[0,40]]+5 (* or *) LinearRecurrence[{2,0,-1},{5,6,6},50] (* Harvey P. Dale, Aug 17 2012 *)
  • PARI
    a(n)=fibonacci(n)+5 \\ Charles R Greathouse IV, Jul 02 2013
    

Formula

G.f.: ( 5-4*x-6*x^2 ) / ( (x-1)*(x^2+x-1) ). - R. J. Mathar, Aug 09 2012
a(0)=5, a(1)=6, a(2)=6, a(n)=2*a(n-1)+0*a(n-2)-a(n-3). - Harvey P. Dale, Aug 17 2012
a(0) = 5, a(1) = 6, a(n) = a(n - 2) + a(n - 1) - 5. - Reinhard Zumkeller, Jul 30 2013

A255870 a(n) is the total number of pentagrams in a pentagram fractal after n iterations.

Original entry on oeis.org

1, 6, 26, 76, 191, 411, 816, 1521, 2726, 4741, 8081, 13566, 22536, 37146, 60896, 99436, 161921, 263151, 427086, 692481, 1122056, 1817281, 2942351, 4762926, 7708866, 12475686, 20188766, 32668996, 52862651, 85536891, 138405156, 223948041, 362359586, 586314421
Offset: 0

Views

Author

Kival Ngaokrajang, Mar 08 2015

Keywords

Comments

Inspired by the "calice" (see detail in the CNRS link).
The pentagrams appearing in the calice are scaled down by a factor of 1/phi = 0.61803398... from the pentagrams whose vertex-to-vertex length = d. See illustration of the nested pentagrams in the links.

Crossrefs

Programs

  • Excel
    See links.
    
  • Magma
    I:=[1,6,26,76,191,411,816]; [n le 7 select I[n] else 3*Self(n-1)-Self(n-2)-4*Self(n-3)+3*Self(n-4)+Self(n-5)-Self(n-6): n in [1..40]]; // Vincenzo Librandi, Mar 18 2015
  • Mathematica
    CoefficientList[Series[(5 x^6 + x^5 - 10 x^4 - 8 x^3 - 9 x^2 - 3 x - 1)/((1-x)^3 (x+1) (x^2+x-1)), {x, 0, 40}], x] (* Vincenzo Librandi, Mar 18 2015 *)
  • PARI
    Vec(-(5*x^6+x^5-10*x^4-8*x^3-9*x^2-3*x-1)/((x-1)^3*(x+1)*(x^2+x-1)) + O(x^100)) \\ Colin Barker, Mar 12 2015
    

Formula

a(n) = 3*a(n-1)-a(n-2)-4*a(n-3)+3*a(n-4)+a(n-5)-a(n-6) for n>6. - Colin Barker, Mar 12 2015
G.f.: -(5*x^6+x^5-10*x^4-8*x^3-9*x^2-3*x-1) / ((x-1)^3*(x+1)*(x^2+x-1)). - Colin Barker, Mar 12 2015
a(n) = (-307 + 5*(-1)^n - 3*2^(2-n)*s*((11-5*s)*(1-s)^n - (1+s)^n*(11+5*s)) - 150*(1+n) - 50*(1+n)*(2+n)) / 8 for n>0 where s=sqrt(5). - Colin Barker, Mar 12 2017
E.g.f.: 3*exp(x/2)*(25*cosh(sqrt(5)*x/2) + 11*sqrt(5)*sinh(sqrt(5)*x/2)) - (12 + 5*x)*(23 + 5*x)*cosh(x)/4 - (281 + 25*x*(7 + x))*sinh(x)/4 - 5. - Stefano Spezia, Dec 07 2022

A079502 Triangle T(n,k) read by rows; related to number of preorders.

Original entry on oeis.org

1, 1, 2, 1, 5, 5, 1, 10, 24, 16, 1, 18, 79, 122, 61, 1, 31, 223, 602, 680, 272, 1, 52, 579, 2439, 4682, 4155, 1385, 1, 86, 1432, 8856, 25740, 38072, 27776, 7936, 1, 141, 3434, 30030, 124146, 272416, 326570, 202084, 50521, 1, 230, 8071, 97332
Offset: 0

Views

Author

N. J. A. Sloane, Jan 21 2003

Keywords

Examples

			Triangle T(n,k) begins:
  1;
  1,  2;
  1,  5,    5;
  1, 10,   24,  16;
  1, 18,   79,  122,    61;
  1, 31,  223,  602,   680,   272;
  1, 52,  579, 2439,  4682,  4155,  1385;
  1, 86, 1432, 8856, 25740, 38072, 27776, 7936;
		

Crossrefs

Diagonals give A000111, A006326, A006327, A006328. Cf. A050447.

Programs

  • Mathematica
    t[n_, m_] := t[n, m] = If[m == 0, 1, t[n, m - 1] + Sum[t[2 k, m - 1] t[n - 1 - 2 k, m], {k, 0, (n - 1)/2}]]; Map[Function[s, Rest@ Reverse@ Map[Abs@ Fold[#2 - #1 &, Reverse@ Take[s, #]] &, Range@ Length@ s]]@ Reverse@ Map[First, NestList[Differences@ # &, {First@ #}~Join~Differences@ #, Length@ # - 2]] &, Table[t[n, k], {n, 2, 11}, {k, 0, n}]] (* Michael De Vlieger, Mar 13 2017, after Jean-François Alcover at A050447 *)

Formula

From Sean A. Irvine, Mar 12 2017: (Start)
A079502 can be constructed one row at a time from the corresponding row of A050447. For row n, construct up to the n-th difference sequence of row n in A050447, retaining the first element of each difference sequence. Row n of A079502 is then constructed backwards (i.e., starting with A079502(n,n) and computing down to A079502(n,2)) from the first element of the n-th difference sequence, then successively subtracting the first element of the previous difference sequences. More precisely, let R_n denote the n-th row of A050447 augmented with R_n(1) = 0, and R_n^(d) the d-th difference of that row, such that R_n^(0)(m) = R_n(m) and R_n^(k)(m) = R_n^(k-1)(m+1) - R_n^(k-1)(m). Row n of A079502 is then T(n,n) = R_n^(n)(0) and for m < n, T(n,m) = R_n^(n)(0) - T(n,m+1).
For example, starting with row 4 of A050447: [0], 1, 8, 31, 85, 190, 371, ..., we construct up to order 4 difference sequences: first-differences 1, 7, 23, 54, 105, 181, ...; second-differences 6, 16, 31, 51, 76, ...; third-differences 10, 15, 20, 25, ...; fourth-differences 5, 5, 5, ... (constant). Only the first elements of these difference sequences are needed. Thus T(4,4) = 5, T(4,3) = 10 - 5 = 5, T(4,2) = 6 - (10 - 5) = 1, T(4,1) = 1 - (6 - (10 - 5)) = 0. (End)

Extensions

More terms from Sean A. Irvine, Mar 12 2017

A180671 a(n) = Fibonacci(n+6) - Fibonacci(6).

Original entry on oeis.org

0, 5, 13, 26, 47, 81, 136, 225, 369, 602, 979, 1589, 2576, 4173, 6757, 10938, 17703, 28649, 46360, 75017, 121385, 196410, 317803, 514221, 832032, 1346261, 2178301, 3524570, 5702879, 9227457, 14930344, 24157809, 39088161, 63245978, 102334147, 165580133
Offset: 0

Views

Author

Johannes W. Meijer, Sep 21 2010

Keywords

Comments

The a(n+1) (terms doubled) are the Kn15 sums of the Fibonacci(n) triangle A104763. See A180662 for information about these knight and other chess sums.

Crossrefs

Cf. A000045.
Cf. A131524 (Kn11), A001911 (Kn12), A006327 (Kn13), A167616 (Kn14), A180671 (Kn15), A180672 (Kn16), A180673 (Kn17), A180674 (Kn18).

Programs

  • GAP
    List([0..40], n-> Fibonacci(n+6)-8); # G. C. Greubel, Jul 13 2019
  • Magma
    [Fibonacci(n+6)-Fibonacci(6): n in [0..40]]; // Vincenzo Librandi, Apr 24 2011
    
  • Maple
    nmax:=40: with(combinat): for n from 0 to nmax do a(n):=fibonacci(n+6)-fibonacci(6) od: seq(a(n),n=0..nmax);
  • Mathematica
    f[n_]:= Fibonacci[n+6] - Fibonacci[6]; Array[f, 40, 0] (* or *)
    LinearRecurrence[{2,0,-1}, {0,5,13}, 41] (* or *)
    CoefficientList[Series[x(3x+5)/(x^3-2x+1), {x,0,40}], x] (* Robert G. Wilson v, Apr 11 2017 *)
  • PARI
    for(n=1,40,print(fibonacci(n+6)-fibonacci(6))); \\ Anton Mosunov, Mar 02 2017
    
  • PARI
    concat(0, Vec(x*(5+3*x)/((1-x)*(1-x-x^2)) + O(x^40))) \\ Colin Barker, Apr 20 2017
    
  • Sage
    [fibonacci(n+6)-8 for n in (0..40)] # G. C. Greubel, Jul 13 2019
    

Formula

a(n) = F(n+6) - F(6) with F = A000045.
a(n) = a(n-1) + a(n-2) + 8 for n>1, a(0)=0, a(1)=5, and where 8 = F(6).
From Colin Barker, Apr 13 2012: (Start)
G.f.: x*(5 + 3*x)/((1 - x)*(1 - x - x^2)).
a(n) = 2*a(n-1) - a(n-3). (End)
a(n) = (-8 + (2^(-n)*((1-sqrt(5))^n*(-9+4*sqrt(5)) + (1+sqrt(5))^n*(9+4*sqrt(5)))) / sqrt(5)). - Colin Barker, Apr 20 2017

A180672 a(n) = Fibonacci(n+7) - Fibonacci(7).

Original entry on oeis.org

0, 8, 21, 42, 76, 131, 220, 364, 597, 974, 1584, 2571, 4168, 6752, 10933, 17698, 28644, 46355, 75012, 121380, 196405, 317798, 514216, 832027, 1346256, 2178296, 3524565, 5702874, 9227452, 14930339, 24157804, 39088156, 63245973
Offset: 0

Views

Author

Johannes W. Meijer, Sep 21 2010

Keywords

Comments

The a(n+1) (terms doubled) are the Kn16 sums of the Fibonacci(n) triangle A104763. See A180662 for information about these knight and other chess sums.

Crossrefs

Cf. A131524 (Kn11), A001911 (Kn12), A006327 (Kn13), A167616 (Kn14), A180671 (Kn15), A180672 (Kn16), A180673 (Kn17), A180674 (Kn18).

Programs

  • GAP
    List([0..40], n-> Fibonacci(n+7)-13 ); # G. C. Greubel, Jul 13 2019
  • Magma
    [Fibonacci(n+7) - Fibonacci(7): n in [0..40]]; // Vincenzo Librandi, Apr 24 2011
    
  • Maple
    nmax:=40: with(combinat): for n from 0 to nmax do a(n):=fibonacci(n+7)-fibonacci(7) od: seq(a(n),n=0..nmax);
  • Mathematica
    Fibonacci[7 +Range[0, 40]] -13 (* G. C. Greubel, Jul 13 2019 *)
  • PARI
    concat(0, Vec(x*(8+5*x)/((1-x)*(1-x-x^2)) + O(x^40))) \\ Colin Barker, Feb 24 2017
    
  • PARI
    a(n)=fibonacci(n+7)-fibonacci(7) \\ Charles R Greathouse IV, Feb 24 2017
    
  • Sage
    [fibonacci(n+7)-13 for n in (0..40)] # G. C. Greubel, Jul 13 2019
    

Formula

a(n) = F(n+7) - F(7) with F = A000045.
a(n) = a(n-1) + a(n-2) + 13 for n>1, a(0)=0, a(1)=8, and where 13 = F(7).
G.f.: x*(8 + 5*x)/((1 - x)*(1 - x - x^2)). - Ilya Gutkovskiy, Feb 24 2017
From Colin Barker, Feb 24 2017: (Start)
a(n) = (-13 + (2^(-1-n)*((1-sqrt(5))^n*(-29+13*sqrt(5)) + (1+sqrt(5))^n*(29+13*sqrt(5)))) / sqrt(5)).
a(n) = 2*a(n-1) - a(n-3) for n>2. (End)
a(n) = 8*A000071(n+2) + 5*A000071(n+1). - Bruno Berselli, Feb 24 2017

A180673 a(n) = Fibonacci(n+8) - Fibonacci(8).

Original entry on oeis.org

0, 13, 34, 68, 123, 212, 356, 589, 966, 1576, 2563, 4160, 6744, 10925, 17690, 28636, 46347, 75004, 121372, 196397, 317790, 514208, 832019, 1346248, 2178288, 3524557, 5702866, 9227444, 14930331, 24157796, 39088148, 63245965, 102334134
Offset: 0

Views

Author

Johannes W. Meijer, Sep 21 2010

Keywords

Comments

The a(n+1) (terms doubled) are the Kn17 sums of the Fibonacci(n) triangle A104763. See A180662 for information about these knight and other chess sums.

Crossrefs

Cf. A131524 (Kn11), A001911 (Kn12), A006327 (Kn13), A167616 (Kn14), A180671 (Kn15), A180672 (Kn16), A180673 (Kn17), A180674 (Kn18).

Programs

  • GAP
    List([0..40], n-> Fibonacci(n+8)-21); # G. C. Greubel, Jul 13 2019
  • Magma
    [Fibonacci(n+8) - Fibonacci(8): n in [0..40]]; // Vincenzo Librandi, Apr 24 2011
    
  • Maple
    nmax:=40: with(combinat): for n from 0 to nmax do a(n):=fibonacci(n+8)-fibonacci(8) od: seq(a(n),n=0..nmax);
  • Mathematica
    Fibonacci[8 +Range[0, 40]] -21 (* G. C. Greubel, Jul 13 2019 *)
  • PARI
    concat(0, Vec(x*(13+8*x)/((1-x)*(1-x-x^2)) + O(x^40))) \\ Colin Barker, Feb 24 2017
    
  • PARI
    a(n)=fibonacci(n+8)-21 \\ Charles R Greathouse IV, Feb 24 2017
    
  • SageMath
    [fibonacci(n+8)-21 for n in (0..40)] # G. C. Greubel, Jul 13 2019
    

Formula

a(n) = F(n+8) - F(8) with F(n) the Fibonacci numbers A000045.
a(n) = a(n-1) + a(n-2) + 21 for n>1, a(0)=0, a(1)=13, and where 21 = F(8).
G.f.: x*(13 + 8*x)/((1 - x)*(1 - x - x^2)). - Ilya Gutkovskiy, Feb 24 2017
a(n) = 13*A000071(n+2) + 8*A000071(n+1). - Bruno Berselli, Feb 24 2017
From Colin Barker, Feb 24 2017: (Start)
a(n) = (-21 + (2^(-1-n)*((1-sqrt(5))^n*(-47+21*sqrt(5)) + (1+sqrt(5))^n*(47+21*sqrt(5)))) / sqrt(5)).
a(n) = 2*a(n-1) - a(n-3) for n>2. (End)

A180674 a(n) = Fibonacci(n+9) - Fibonacci(9).

Original entry on oeis.org

0, 21, 55, 110, 199, 343, 576, 953, 1563, 2550, 4147, 6731, 10912, 17677, 28623, 46334, 74991, 121359, 196384, 317777, 514195, 832006, 1346235, 2178275, 3524544, 5702853, 9227431, 14930318, 24157783, 39088135, 63245952, 102334121
Offset: 0

Views

Author

Johannes W. Meijer, Sep 21 2010

Keywords

Comments

The a(n+1) (terms doubled) are the Kn18 sums of the Fibonacci(n) triangle A104763. See A180662 for information about these knight and other chess sums.

Crossrefs

Cf. A131524 (Kn11), A001911 (Kn12), A006327 (Kn13), A167616 (Kn14), A180671 (Kn15), A180672 (Kn16), A180673 (Kn17), A180674 (Kn18).

Programs

  • GAP
    List([0..40], n-> Fibonacci(n+9)-34); # G. C. Greubel, Jul 13 2019
  • Magma
    [Fibonacci(n+9) - Fibonacci(9): n in [0..40]]; // Vincenzo Librandi, Apr 24 2011
    
  • Maple
    nmax:=31: with(combinat): for n from 0 to nmax do a(n):=fibonacci(n+9)-fibonacci(9) od: seq(a(n),n=0..nmax);
  • Mathematica
    Fibonacci[9 +Range[0, 40]] -34 (* G. C. Greubel, Jul 13 2019 *)
    LinearRecurrence[{2,0,-1},{0,21,55},40] (* Harvey P. Dale, Aug 24 2024 *)
  • PARI
    concat(0, Vec(x*(21+13*x)/((1-x)*(1-x-x^2)) + O(x^40))) \\ Colin Barker, Feb 24 2017
    
  • PARI
    a(n) = fibonacci(n+9) - fibonacci(9) \\ Charles R Greathouse IV, Feb 24 2017
    
  • Sage
    [fibonacci(n+9)-34 for n in (0..40)] # G. C. Greubel, Jul 13 2019
    

Formula

a(n) = F(n+9) - F(9) with F = A000045.
a(n) = a(n-1) + a(n-2) + 34 for n>1, a(0)=0, a(1)=21, and where 34 = F(9).
G.f.: x*(21 + 13*x)/((1 - x)*(1 - x - x^2)). - Ilya Gutkovskiy, Feb 24 2017
a(n) = 21*A000071(n+2) + 13*A000071(n+1). - Bruno Berselli, Feb 24 2017
From Colin Barker, Feb 24 2017: (Start)
a(n) = (-34 + (2^(-n)*((1-sqrt(5))^n*(-38+17*sqrt(5)) + (1+sqrt(5))^n*(38+17*sqrt(5)))) / sqrt(5)).
a(n) = 2*a(n-1) - a(n-3) for n>2. (End)

A256107 Irregular triangle read by rows, T(n,k) is the number of pentagrams on the k layers at n iterations of a pentagram fractal (see comment).

Original entry on oeis.org

1, 2, 4, 1, 7, 2, 2, 12, 4, 5, 2, 1, 20, 7, 10, 4, 2, 2, 33, 12, 18, 8, 4, 4, 2, 1, 54, 20, 31, 14, 7, 8, 4, 2, 2, 88, 33, 52, 24, 12, 14, 8, 4, 4, 2, 1, 143, 54, 86, 40, 20, 24, 14, 7, 8, 4, 2, 2, 232, 88, 141, 66, 33, 40, 24, 12, 14, 8, 4, 4, 2, 1, 376, 143, 230, 108, 54, 66
Offset: 0

Views

Author

Kival Ngaokrajang, Mar 14 2015

Keywords

Comments

Refer to A255870, the number of pentagrams on one side of the outer layer (including pentagrams on two vertices) at n iterations would be T(n,0), the next layers k >= 1 T(n,k) are the number of pentagrams toward the center. For k >= 2, the row length is A032766. The first differences of A255870 = 5*(rows sum - 1). T(n,k) = A000071 with a shift for k = 0 or k mod 3 = 1. T(n,2) = A006327 with a shift. For k >= 3, T(n,k) = 2*A000071 with a shift for k mod 3 = 0 or 2. See illustration in the links.

Examples

			Irreuglar triangle begins:
n/k  0  1  2  3  4  5  6  7  8 ...
0   1
1   2
2   4  1
3   7  2  2
4  12  4  5  2  1
5  20  7 10  4  2  2
6  33 12 18  8  4  4  2  1
7  54 20 31 14  7  8  4  2  2
8  88 33 52 24 12 14  8  4  4
...
		

Crossrefs

Programs

  • PARI
    {for(n=0, 20, if(n<2, lk=0, lk=floor(3*(n-2)/2)+1); for (k=0, lk, if(k<>0, if(k<>2, if(Mod(k,3)==1, t=fibonacci(n+1-2*(k-1)/3)-1, t=2*(fibonacci(n+2-ceil((2*k+1)/3))-1)), t=fibonacci(n+2)-3), t=fibonacci(n+3-2*k/3)-1); print1(t, ", ")))}
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