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.

A181722 Numerator of (1/n - Bernoulli number A164555(n)/A027642(n)).

Original entry on oeis.org

0, 0, 1, 1, 7, 1, 5, 1, 13, 1, 1, 1, 901, 1, -11, 1, 3647, 1, -43825, 1, 1222387, 1, -854507, 1, 1181821001, 1, -76977925, 1, 23749461059, 1, -8615841275543, 1, 28267510484519, 1
Offset: 1

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Author

Paul Curtz, Nov 17 2010

Keywords

Comments

An autosequence is a sequence whose inverse binomial transform is the sequence signed. In integers, the oldest example is Fibonacci A000045. In fractions, A164555/A027642 is the son of 1/n via the Akiyama-Tanigawa algorithm; grandson is (A174110/A174111) = 1/2, 2/3, 1/2, 2/15, ...; see A164020. See A174341/A174342. All are from the same family.

Examples

			Fractions are 0, 0, 1/6, 1/4, 7/30, 1/6, 5/42, 1/8, 13/90, 1/10, 1/66, 1/12, 901/2730, ...
		

Crossrefs

Programs

  • Magma
    A181722:= func< n | n le 2 select 0 else Numerator(1/n - Bernoulli(n-1)) >;
    [A181722(n): n in [1..40]]; // G. C. Greubel, Mar 25 2024
    
  • Mathematica
    a[n_] := If[n <= 2, 0, Numerator[1/n - BernoulliB[n-1]]];
    Table[a[n], {n, 1, 34}] (* Jean-François Alcover, Jun 07 2017 *)
  • SageMath
    def A181722(n): return 0 if n<3 else numerator(1/n - bernoulli(n-1))
    [A181722(n) for n in range(1,41)] # G. C. Greubel, Mar 25 2024

A174111 Denominators of the image of a modified Bernoulli-number sequence under the Akiyama-Tanigawa transform.

Original entry on oeis.org

2, 3, 2, 15, 6, 7, 6, 15, 10, 33, 6, 455, 210, 3, 2, 255, 30, 133, 42, 33, 110, 69, 6, 455, 546, 3, 2, 435, 30, 2387, 462
Offset: 0

Views

Author

Paul Curtz, Mar 08 2010

Keywords

Comments

The image of the sequence A164555(k)/A027642(k), k>=0, under the Takiyama-Tanigawa
transform is
1/2, 2/3, 1/2, 2/15, -1/6, -1/7, 1/6, 4/15, -3/10, -25/33, 5/6, 1382/455, -691/210, -49/3, 35/2, 28936/255, -3617/30, -131601/133, 43867/42, 349222/33, ...
The current sequence contains the denominators of this image.

Crossrefs

Cf. A174110 (numerators), A164661.

Programs

  • Maple
    read("transforms3") ;
    A174111 := proc(n) Lin := [bernoulli(0),-bernoulli(1),seq(bernoulli(k),k=2..n+1)] ; AKIYATANI(Lin) ; denom(op(n+1,%)) ; end proc:
  • Mathematica
    b[0]=0; b[1]=1; b[2]=1/2; b[n_] := BernoulliB[n-1]; a[0, m_] := b[m+1]; a[n_, m_] := a[n, m] = (m+1)*(a[n-1, m] - a[n-1, m+1]); Table[a[1, m], {m, 0, 30}] // Denominator  (* Jean-François Alcover, Aug 09 2012 *)

A174129 Numerators of the first column of the table of fractions generated by the Akiyama-Tanigawa transform from a first row A164555(k)/A027642(k).

Original entry on oeis.org

1, 1, -1, -1, 31, 7, -1051, -201, 56911, 18311, -24346415, -4227881, 425739604981, 2082738855, -759610463437, -1935668684041, 91825384886337407, 3104887811293639, -333936446105326262497, -8039608511660213481, 496858217433153341005061
Offset: 0

Views

Author

Paul Curtz, Mar 09 2010

Keywords

Comments

The first 6 rows if the table generated by iterative application of the Akiyama-Tanigawa transform starting with a header row of fractions A164555(k)/A027642(k) are:
1, 1/2, 1/6, 0, -1/30, 0, 1/42, 0, -1/30, 0, 5/66, 0, -691/2730, 0, 7/6, ...
1/2, 2/3, 1/2, 2/15, -1/6, -1/7, 1/6, 4/15, -3/10, -25/33, 5/6, 1382/455, ...
-1/6, 1/3, 11/10, 6/5, -5/42, -13/7, -7/10, 68/15, 453/110, -175/11, ...
-1/2, -23/15, -3/10, 554/105, 365/42, -243/35, -1099/30, 548/165, 19827/110, ...
31/30, -37/15, -1171/70, -478/35, 469/6, 1247/7, -6153/22, -46708/33, ...
7/2, 599/21, -129/14, -38566/105, -20995/42, 211515/77, 524699/66, ...
The numerators of the leftmost column define the current sequence.

Crossrefs

Cf. A141056 (denominators), A174110, A174111 (first row).

Programs

  • Maple
    read("transforms3") ;
    A174129 := proc(n) Lin := [bernoulli(0),-bernoulli(1),seq(bernoulli(k),k=2..n+1)] ; for r from 1 to n do Lin := AKIYATANI(Lin) ; end do; numer(op(1,Lin)) ; end proc:
  • Mathematica
    a[0, k_] := a[0, k] = BernoulliB[k]; a[0, 1] = 1/2; a[n_, k_] := a[n, k] = (k+1)*(a[n-1, k] - a[n-1, k+1]); a[n_] := a[n, 0] // Numerator; Table[a[n], {n, 0, 20}] (* Jean-François Alcover, Aug 14 2012 *)

Formula

a(n) = numerator(Sum_{j=0..n} (-1)^(n-j)*j!*Stirling2(n,j)*B(j)), where B are the Bernoulli numbers A164555/A027642. - Fabián Pereyra, Jan 06 2022
Showing 1-3 of 3 results.