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 1-3 of 3 results.

A134940 Define f(n) by e(n+1) = e(n) + 3^{n+1} - 1 + 2*f(n), where the rational numbers e(n) are defined in A134939; then a(n) is the numerator of f(n).

Original entry on oeis.org

0, 17, 424, 7889, 131920, 2099537, 32570104, 498191249, 7559339680, 114166849937, 1719485965384, 25855100073809, 388391603257840, 5830958998038737, 87510144649440664, 1313063982494679569, 19699665930299694400, 295528344080575921937, 4433225354293155251944
Offset: 0

Views

Author

Toby Berger (tb6n(AT)virginia.edu), Jan 23 2008

Keywords

Examples

			The values of f(0), ..., f(3) are 0, 17/3, 424/9, 7889/27.
		

Crossrefs

Cf. A134939.

Formula

f(n) = (6*3^n-1)*(5^n-3^n)/(2*3^n); a(n) = (6*3^n-1)*(5^n-3^n)/2. - Max Alekseyev, Feb 04 2008
G.f.: x*(135*x^2-120*x+17) / ((3*x-1)*(5*x-1)*(9*x-1)*(15*x-1)). - Colin Barker, Dec 26 2012

Extensions

Values of f(4) onwards and a general formula found by Max Alekseyev, Feb 02 2008, Feb 04 2008

A007798 Expected number of random moves in Tower of Hanoi problem with n disks starting with a randomly chosen position and ending at a position with all disks on the same peg.

Original entry on oeis.org

0, 0, 2, 18, 116, 660, 3542, 18438, 94376, 478440, 2411882, 12118458, 60769436, 304378620, 1523487422, 7622220078, 38125449296, 190670293200, 953480606162, 4767790451298, 23840114517956, 119204059374180, 596030757224102, 2980185167180118, 14901019979079416
Offset: 0

Views

Author

David G. Poole (dpoole(AT)trentu.ca)

Keywords

Comments

All 3^n possible starting positions are chosen with equal probability.

Crossrefs

Partial sums of A005058.
Cf. A134939.

Programs

  • Magma
    [(5^n-2*3^n+1)/4: n in [0..25]]; // Vincenzo Librandi, Oct 11 2011
    
  • Maple
    seq( (1 -2*3^n +5^n)/4, n=0..25); # G. C. Greubel, Mar 05 2020
  • Mathematica
    Table[(1 -2*3^n +5^n)/4, {n,0,25}] (* G. C. Greubel, Mar 05 2020 *)
  • PARI
    concat([0,0], Vec(-2*x^2/((x-1)*(3*x-1)*(5*x-1)) + O(x^30))) \\ Colin Barker, Sep 17 2014
    
  • Sage
    [(1 -2*3^n +5^n)/4 for n in (0..25)] # G. C. Greubel, Mar 05 2020

Formula

For n>1, a(n) = 8*a(n-1) - 15*a(n-2) + 2 = 2*A016209(n-2). - Henry Bottomley, Jun 06 2000
a(n) = (5^n - 2*3^n + 1) / 4. - Henry Bottomley, Jun 06 2000, proved by Max Alekseyev, Feb 04 2008
From Colin Barker, Sep 17 2014: (Start)
a(n) = 9*a(n-1) - 23*a(n-2) + 15*a(n-3).
G.f.: 2*x^2/((1-x)*(1-3*x)*(1-5*x)). (End)
E.g.f.: (exp(x) - 2*exp(3*x) + exp(5*x))/4. - G. C. Greubel, Mar 05 2020

Extensions

More precise definition and more terms from Max Alekseyev, Feb 04 2008
a(0)=0 prepended by Max Alekseyev, Sep 08 2014

A246961 Numerator of the expected number of random moves in Tower of Hanoi problem with n disks starting at a randomly chosen valid configuration and ending with all disks at peg 1.

Original entry on oeis.org

0, 4, 146, 3034, 52916, 857824, 13426406, 206324374, 3138660776, 47471139964, 715573119866, 10765074628114, 161759034582236, 2428929817996504, 36456836245518926, 547058495778290254, 8207730761823753296, 123132640134289171444, 1847139704277091999586, 27708446454015214334794, 415638854666404701309956
Offset: 0

Views

Author

Max Alekseyev, Sep 08 2014

Keywords

Comments

The expected number of random moves is given by a(n)/3^n = a(n)/A000244(n).

Crossrefs

Programs

  • PARI
    concat(0, Vec(-2*x*(135*x^2-9*x-2)/((3*x-1)*(5*x-1)*(9*x-1)*(15*x-1)) + O(x^100))) \\ Colin Barker, Sep 17 2014

Formula

a(n) = ( (3^n - 1)*(5^(n+1) - 2*3^(n+1)) + 5^n - 3^n ) / 4.
a(n) = 3^n*A007798(n) + 2*A134939(n).
G.f.: -2*x*(135*x^2-9*x-2) / ((3*x-1)*(5*x-1)*(9*x-1)*(15*x-1)). - Colin Barker, Sep 17 2014
Showing 1-3 of 3 results.