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 1-5 of 5 results.

A078921 Signed variant of A077012.

Original entry on oeis.org

1, -1, 2, 2, -3, 6, -6, 8, -12, 24, 24, -30, 40, -60, 120, -120, 144, -180, 240, -360, 720, 720, -840, 1008, -1260, 1680, -2520, 5040, -5040, 5760, -6720, 8064, -10080, 13440, -20160, 40320, 40320, -45360, 51840, -60480, 72576, -90720, 120960, -181440, 362880, -362880, 403200, -453600, 518400, -604800, 725760, -907200, 1209600, -1814400, 3628800
Offset: 1

Views

Author

Wouter Meeussen, Dec 14 2002

Keywords

Comments

Row sums give A024167.

Examples

			Triangle starts:
     1
    -1,    2
     2,   -3,    6
    -6,    8,  -12,    24
    24,  -30,   40,   -60,  120
  -120,  144, -180,   240, -360,   720
   720, -840, 1008, -1260, 1680, -2520, 5040
  ...
		

Crossrefs

Programs

  • Mathematica
    Table[Table[ -(-1)^(n-k+1) n/(n-k+1), {k, 1, n}] (n-1)!, {n, 1, 12}]

Formula

T(n, k) = -(-1)^(n-k+1)*(n/(n-k+1))*(n-1)!.
E.g.f.: log(1+x)/(1-y*x). - Vladeta Jovovic, Feb 07 2003
Sum_{n>=1} Sum_{k=1..n} 1/T(n, k) = (e^2+1)/(4*e). - Amiram Eldar, Jun 29 2025

A166350 Triangle read by rows: T(n,m) = m!, n >= 1.

Original entry on oeis.org

1, 1, 2, 1, 2, 6, 1, 2, 6, 24, 1, 2, 6, 24, 120, 1, 2, 6, 24, 120, 720, 1, 2, 6, 24, 120, 720, 5040, 1, 2, 6, 24, 120, 720, 5040, 40320, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, 3628800, 1, 2, 6, 24, 120, 720, 5040, 40320
Offset: 1

Views

Author

Paul Curtz, Oct 12 2009

Keywords

Examples

			Triangle begins:
  1;
  1, 2;
  1, 2, 6;
  1, 2, 6, 24;
  1, 2, 6, 24, 120;
  1, 2, 6, 24, 120, 720;
  1, 2, 6, 24, 120, 720, 5040;
  ...
		

Crossrefs

Cf. A014454.
Row sums give A007489.

Programs

  • Haskell
    import Data.List (inits)
    a166350 n k = a166350_tabl !! (n-1) !! (n-1)
    a166350_row n = a166350_tabl !! (n-1)
    a166350_tabl = tail $ inits $ tail a000142_list
    -- Reinhard Zumkeller, Nov 11 2013
  • Mathematica
    Flatten[Table[Range[n]!,{n,11}]] (* Harvey P. Dale, Jan 06 2012 *)
    Module[{nn=20,fs},fs=Range[nn]!;Table[Take[fs,n],{n,nn}]]//Flatten (* Harvey P. Dale, Jun 14 2020 *)

Formula

T(n,m) = A000142(m).

Extensions

Definition clarified - R. J. Mathar, Oct 14 2009

A058298 Triangle n!/(n-k), 1 <= k < n, read by rows.

Original entry on oeis.org

2, 3, 6, 8, 12, 24, 30, 40, 60, 120, 144, 180, 240, 360, 720, 840, 1008, 1260, 1680, 2520, 5040, 5760, 6720, 8064, 10080, 13440, 20160, 40320, 45360, 51840, 60480, 72576, 90720, 120960, 181440, 362880, 403200, 453600, 518400, 604800, 725760, 907200, 1209600, 1814400, 3628800
Offset: 2

Views

Author

Leroy Quet, Dec 07 2000

Keywords

Comments

Together with 1, numbers n such that n divides k! if and only if k! >= n. - Charles R Greathouse IV, Aug 16 2016

Examples

			Triangle begins:
      2;
      3,     6;
      8,    12,    24;
     30,    40,    60,   120;
    144,   180,   240,   360,   720;
    840,  1008,  1260,  1680,  2520,   5040;
   5760,  6720,  8064, 10080, 13440,  20160,  40320;
  45360, 51840, 60480, 72576, 90720, 120960, 181440, 362880;
  ...
		

Crossrefs

Columns k=1..5 are A001048(n-1), A052747, A052759, A052778, A052794.
Row sums are A052881.

Programs

  • Mathematica
    Flatten[Table[n!/(n-k),{n,2,10},{k,n-1}]] (* Harvey P. Dale, Jul 23 2014 *)
  • PARI
    T(n,k)={if(kAndrew Howroyd, Aug 08 2020

Formula

Sum_{n>=2} Sum_{k=1..n-1} 1/T(n, k) = e/2 (A019739). - Amiram Eldar, Jun 29 2025

A335442 List enumerated in lexicographic order of (n, s, k), where for each n >= 1, for each s a subset of 1..n with n-1 elements, and for each k in 0..n-1, we give the value of (Sum_{t subset of s, Card(t)=k} Product_{x in t} x).

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 3, 2, 1, 4, 3, 1, 5, 6, 1, 6, 11, 6, 1, 7, 14, 8, 1, 8, 19, 12, 1, 9, 26, 24, 1, 10, 35, 50, 24, 1, 11, 41, 61, 30, 1, 12, 49, 78, 40, 1, 13, 59, 107, 60, 1, 14, 71, 154, 120, 1, 15, 85, 225, 274, 120, 1, 16, 95, 260, 324, 144, 1, 17, 107, 307, 396, 180, 1, 18, 121, 372, 508, 240, 1, 19, 137, 461, 702, 360, 1, 20, 155, 580, 1044, 720
Offset: 1

Views

Author

Luc Rousseau, Jun 10 2020

Keywords

Comments

This sequence can be viewed as a triangle made of square blocks of increasing sizes: 1 X 1, 2 X 2, and so on. In block number n >= 1, the bottom-right corner is n!, the top-right one (n-1)!. The first row of block number n, which is row number binomial(n, 2) if we number the rows according to their second value, is the list of the unsigned Stirling numbers of the first kind, reversed. The subsequence {last element of row n} is A077012.
Block number n crops up for instance when studying -log(1-r), where r = e^(i*2*Pi/n); this is Sum_{K>=1} r^K/K = Sum_{K>=0} Sum_{L=1..n} r^L/(nK+L);
the term for K in the first sum, if put in the same denominator and if no simplification is carried out, has a numerator which is a combination of all (nK)^I * r^J; their coefficients are precisely the elements of block number n.

Examples

			Table begins:
  +---+
  | 1 |
  +---+----+
  | 1    1 |
  | 1    2 |
  +--------+----+
  | 1    3    2 |
  | 1    4    3 |
  | 1    5    6 |
  +-------------+----+
  | 1    6   11    6 |
  | 1    7   14    8 |
  | 1    8   19   12 |
  | 1    9   26   24 |
  +------------------+----+
  | 1   10   35   50   24 |
  | 1   11   41   61   30 |
  | 1   12   49   78   40 |
  | 1   13   59  107   60 |
  | 1   14   71  154  120 |
  +-----------------------+----+
  | 1   15   85  225  274  120 |
  | 1   16   95  260  324  144 |
  | 1   17  107  307  396  180 |
  | 1   18  121  372  508  240 |
  | 1   19  137  461  702  360 |
  | 1   20  155  580 1044  720 |
  +----------------------------+----+
  | 1   21  175  735 1624 1764  720 |
  | 1   22  190  820 1849 2038  840 |
  | 1   23  207  925 2144 2412 1008 |
  | 1   24  226 1056 2545 2952 1260 |
  | 1   25  247 1219 3112 3796 1680 |
  | 1   26  270 1420 3929 5274 2520 |
  | 1   27  295 1665 5104 8028 5040 |
  +---------------------------------+----+
  etc.
		

Crossrefs

A165969 Triangle read by rows: T(n,m) = A094310(n,m)*A120070(n+1,m), 1 <= m <= n.

Original entry on oeis.org

3, 16, 5, 90, 36, 14, 576, 252, 128, 54, 4200, 1920, 1080, 600, 264, 34560, 16200, 9600, 5940, 3456, 1560, 317520, 151200, 92400, 60480, 39312, 23520, 10800, 3225600, 1552320, 967680, 655200, 451584, 302400, 184320, 85680, 35925120, 17418240, 11007360, 7620480, 5443200, 3870720, 2643840, 1632960, 766080
Offset: 1

Views

Author

Paul Curtz, Oct 02 2009

Keywords

Comments

The second array mentioned in the comment in A129326.

Examples

			Triangle begins
        3;
       16,       5;
       90,      36,     14;
      576,     252,    128,     54;
     4200,    1920,   1080,    600,    264;
    34560,   16200,   9600,   5940,   3456,   1560;
   317520,  151200,  92400,  60480,  39312,  23520,  10800;
  3225600, 1552320, 967680, 655200, 451584, 302400, 184320, 85680;
		

Crossrefs

Programs

Showing 1-5 of 5 results.