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.

A000738 Boustrophedon transform (first version) of Fibonacci numbers 0,1,1,2,3,...

Original entry on oeis.org

0, 1, 3, 8, 25, 85, 334, 1497, 7635, 43738, 278415, 1949531, 14893000, 123254221, 1098523231, 10490117340, 106851450165, 1156403632189, 13251409502982, 160286076269309, 2040825708462175, 27283829950774822, 382127363497453243, 5595206208670390323
Offset: 0

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Author

Keywords

Crossrefs

Programs

  • Haskell
    a000738 n = sum $ zipWith (*) (a109449_row n) a000045_list
    -- Reinhard Zumkeller, Nov 03 2013
    
  • Maple
    read(transforms);
    with(combinat):
    F:=fibonacci;
    [seq(F(n),n=0..50)];
    BOUS2(%);
  • Mathematica
    FullSimplify[CoefficientList[Series[(2/Sqrt[5]) * E^(x/2) * (E^(Sqrt[5]/2*x)/2 - E^(-Sqrt[5]/2*x)/2) * (Sin[x]+1) / Cos[x], {x, 0, 20}], x]* Range[0, 20]!] (* Vaclav Kotesovec after Alois P. Heinz, Oct 05 2013 *)
    t[n_, 0] := Fibonacci[n]; t[n_, k_] := t[n, k] = t[n, k-1] + t[n-1, n-k]; a[n_] := t[n, n]; Array[a, 30, 0] (* Jean-François Alcover, Feb 12 2016 *)
  • Python
    from itertools import islice, accumulate
    def A000738_gen(): # generator of terms
        blist, a, b = tuple(), 0, 1
        while True:
            yield (blist := tuple(accumulate(reversed(blist),initial=a)))[-1]
            a, b = b, a+b
    A000738_list = list(islice(A000738_gen(),30)) # Chai Wah Wu, Jun 11 2022

Formula

E.g.f.: (2/sqrt(5)) * exp(x/2) * sinh((sqrt(5)/2)*x) * (sin(x)+1) / cos(x). - Alois P. Heinz, Feb 08 2011
a(n) ~ 4*(exp(sqrt(5)*Pi/2)-1) * (2*n/Pi)^(n+1/2) * exp(Pi/4-n-sqrt(5)*Pi/4) / sqrt(5). - Vaclav Kotesovec, Oct 05 2013
a(n) = sum(A109449(n,k)*A000045(k): k=0..n). - Reinhard Zumkeller, Nov 03 2013

Extensions

Entry revised by N. J. A. Sloane, Mar 16 2011

A000744 Boustrophedon transform (second version) of Fibonacci numbers 1,1,2,3,...

Original entry on oeis.org

1, 2, 5, 14, 42, 144, 563, 2526, 12877, 73778, 469616, 3288428, 25121097, 207902202, 1852961189, 17694468210, 180234349762, 1950592724756, 22352145975707, 270366543452702, 3442413745494957, 46021681757269830
Offset: 0

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Author

Keywords

Examples

			G.f. = 1 + 2*x + 5*x^2 + 14*x^3 + 42*x^4 + 144*x^5 + 563*x^6 + 2526*x^7 + ...
		

Crossrefs

Programs

  • Haskell
    a000744 n = sum $ zipWith (*) (a109449_row n) $ tail a000045_list
    -- Reinhard Zumkeller, Nov 03 2013
    
  • Maple
    read(transforms);
    with(combinat):
    F:=fibonacci;
    [seq(F(n), n=1..50)];
    BOUS2(%);
  • Mathematica
    s[k_] := SeriesCoefficient[(1 + Sin[x])/Cos[x], {x, 0, k}] k!;
    b[n_, k_] := Binomial[n, k] s[n - k];
    a[n_] := Sum[b[n, k] Fibonacci[k + 1], {k, 0, n}];
    Array[a, 22, 0] (* Jean-François Alcover, Jun 01 2019 *)
  • Python
    from itertools import accumulate, islice
    def A000744_gen(): # generator of terms
        blist, a, b = tuple(), 1, 1
        while True:
            yield (blist := tuple(accumulate(reversed(blist),initial=a)))[-1]
            a, b = b, a+b
    A000744_list = list(islice(A000744_gen(),40)) # Chai Wah Wu, Jun 12 2022

Formula

a(n) = Sum_{k=0..n} A109449(n,k)*A000045(k+1). - Reinhard Zumkeller, Nov 03 2013
E.g.f.: (1/10)*(sec(x)+tan(x))*((5^(1/2)+1)*exp(1/2*x*(5^(1/2)+1))+(5^(1/2)-1)*exp(1/2*x*(-5^(1/2)+1)))*5^(1/2). - Sergei N. Gladkovskii, Oct 30 2014
a(n) ~ n! * (sqrt(5) - 1 + (1+sqrt(5)) * exp(sqrt(5)*Pi/2)) * 2^(n+1) / (sqrt(5) * exp((sqrt(5)-1)*Pi/4) * Pi^(n+1)). - Vaclav Kotesovec, Jun 12 2015

Extensions

Entry revised by N. J. A. Sloane, Mar 16 2011

A000687 Boustrophedon transform (first version) of Fibonacci numbers 0,1,1,2,3,5,...

Original entry on oeis.org

1, 1, 2, 6, 17, 59, 229, 1029, 5242, 30040, 191201, 1338897, 10228097, 84647981, 754437958, 7204350870, 73382899597, 794189092567, 9100736472725, 110080467183393, 1401588037032782, 18737851806495008, 262435512896178877
Offset: 0

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Author

Keywords

Examples

			From _John Cerkan_, Jan 25 2017: (Start)
The array begins:
                1
             0  ->  1
          2  <- 2   <-  1
       1  -> 3  ->  5   ->  6
  17  <- 16  <- 13  <-  8   <- 2 (End)
		

Crossrefs

Programs

  • Maple
    read(transforms);
    with(combinat):
    F:=fibonacci;
    [seq(F(n),n=0..50)];
    BOUS(%);

Formula

E.g.f.: (sec(x) + tan(x))*(((exp(a*x) - 1)/a - (exp(b*x) - 1)/b)/(a - b) + 1), where a = (1 + sqrt(5))/2 and b = (1 - sqrt(5))/2. - Petros Hadjicostas, Feb 16 2021

Extensions

Entry revised by N. J. A. Sloane, Mar 15 2011

A092090 Boustrophedon transform of Fibonacci numbers 1, 2, 3, 5, 8, ...

Original entry on oeis.org

1, 3, 8, 22, 67, 229, 897, 4023, 20512, 117516, 748031, 5237959, 40014097, 331156423, 2951484420, 28184585550, 287085799927, 3106996356945, 35603555478689, 430652619722011, 5483239453957132, 73305511708044652, 1026690239891085363, 15033060056592047307
Offset: 0

Views

Author

N. J. A. Sloane, Apr 01 2004

Keywords

Crossrefs

Cf. A000744 (which uses BOUS2), A062122 (which uses Fibonacci numbers with an error in them), A092073.

Programs

  • Maple
    read transforms; with(combinat, fibonacci): a := [seq(fibonacci(i),i=2..30)]: BOUS2(a);
  • Python
    from itertools import accumulate, islice
    def A092090_gen(): # generator of terms
        blist, a, b = tuple(), 1, 2
        while True:
            yield (blist := tuple(accumulate(reversed(blist),initial=a)))[-1]
            a, b = b, a+b
    A092090_list = list(islice(A092090_gen(),40)) # Chai Wah Wu, Jun 12 2022

Formula

E.g.f.: (sec(x) + tan(x))*(a^2*exp(a*x) - b^2*exp(b*x))/(a - b), where a = (1 + sqrt(5))/2 and b = (1 - sqrt(5))/2. - Petros Hadjicostas, Feb 16 2021
Showing 1-4 of 4 results.