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 11-16 of 16 results.

A151576 Number of permutations of 1..n arranged in a circle with exactly 3 adjacent element pairs in decreasing order.

Original entry on oeis.org

0, 4, 55, 396, 2114, 9528, 38637, 146080, 526240, 1831644, 6217523, 20716164, 68059710, 221195824, 712856665, 2282058360, 7266358556, 23035517940, 72760054815, 229112753980, 719545590010, 2254604460264, 7050252659525, 22006821057936, 68581455012504, 213411502891468
Offset: 3

Views

Author

R. H. Hardin, May 21 2009

Keywords

Comments

Exactly 2 adjacent element pairs in decreasing order gives A027540(n-1).

Crossrefs

Column k=3 of A334218.
Related sequences: A151577-A151610.
Cf. A000460.

Programs

  • PARI
    a(n)={n*(3^(n-1) - n*2^(n-1) + n*(n-1)/2)} \\ Andrew Howroyd, May 05 2020

Formula

From Andrew Howroyd, May 05 2020: (Start)
a(n) = n*A000460(n-1).
a(n) = n*(3^(n-1) - n*2^(n-1) + n*(n-1)/2).
a(n) = 16*a(n-1) - 111*a(n-2) + 438*a(n-3) - 1083*a(n-4) + 1740*a(n-5) - 1817*a(n-6) + 1190*a(n-7) - 444*a(n-8) + 72*a(n-9).
G.f.: x^4*(4 - 9*x - 40*x^2 + 131*x^3 - 98*x^4)/((1 - x)^4*(1 - 2*x)^3*(1 - 3*x)^2).
(End)

Extensions

Terms a(18) and beyond from Andrew Howroyd, May 05 2020

A293616 Array of generalized Eulerian number triangles read by ascending antidiagonals, with m >= 0, n >= 0 and 0 <= k <= n.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 3, 0, 0, 1, 6, 0, 1, 0, 1, 10, 0, 7, 1, 0, 1, 15, 0, 25, 4, 0, 0, 1, 21, 0, 65, 10, 0, 1, 0, 1, 28, 0, 140, 20, 0, 15, 4, 0, 1, 36, 0, 266, 35, 0, 90, 30, 1, 0, 1, 45, 0, 462, 56, 0, 350, 120, 5, 0, 0, 1, 55, 0, 750, 84, 0, 1050, 350, 15, 0, 1, 0
Offset: 0

Views

Author

Peter Luschny, Oct 14 2017

Keywords

Examples

			Array starts:
m\j| 0   1  2     3    4  5       6       7    8  9      10      11      12
---|----------------------------------------------------------------------------
m=0| 1,  0, 0,    0,   0, 0,      0,      0,   0, 0,      0,      0,      0, ...
m=1| 1,  1, 0,    1,   1, 0,      1,      4,   1, 0,      1,     11,     11, ...
m=2| 1,  3, 0,    7,   4, 0,     15,     30,   5, 0,     31,    146,     91, ...
m=3| 1,  6, 0,   25,  10, 0,     90,    120,  15, 0,    301,    896,    406, ...
m=4| 1, 10, 0,   65,  20, 0,    350,    350,  35, 0,   1701,   3696,   1316, ...
m=5| 1, 15, 0,  140,  35, 0,   1050,    840,  70, 0,   6951,  11886,   3486, ...
m=6| 1, 21, 0,  266,  56, 0,   2646,   1764, 126, 0,  22827,  32172,   8022, ...
m=7| 1, 28, 0,  462,  84, 0,   5880,   3360, 210, 0,  63987,  76692,  16632, ...
m=8| 1, 36, 0,  750, 120, 0,  11880,   5940, 330, 0, 159027, 165792,  31812, ...
m=9| 1, 45, 0, 1155, 165, 0,  22275,   9900, 495, 0, 359502, 331617,  57057, ...
   A000217, A001296,A000292,A001297,A027789,A000332,A001298,A293610,A293611, ...
.
m\j| ...    13  14      15       16       17      18      19 20
---|----------------------------------------------------------------
m=0| ...,    0, 0,       0,       0,       0,      0,      0, 0, ...  [A000007]
m=1| ...,    1, 0,       1,      26,      66,     26,      1, 0, ...  [A173018]
m=2| ...,    6, 0,      63,     588,     868,    238,      7, 0, ...  [A062253]
m=3| ...,   21, 0,     966,    5376,    5586,   1176,     28, 0, ...  [A062254]
m=4| ...,   56, 0,    7770,   30660,   24570,   4200,     84, 0, ...  [A062255]
m=5| ...,  126, 0,   42525,  129780,   84630,  12180,    210, 0, ...
m=6| ...,  252, 0,  179487,  446292,  245322,  30492,    462, 0, ...
m=7| ...,  462, 0,  627396, 1315776,  625086,  68376,    924, 0, ...
m=8| ...,  792, 0, 1899612, 3444012, 1440582, 140712,   1716, 0, ...
m=9| ..., 1287, 0, 5135130, 8198190, 3063060, 270270,   3003, 0, ...
          A000389, A112494, A293612, A293613,A293614,A000579.
.
The parameter m runs over the triangles and j indexes the triangles by reading them by rows. Let T(m, n) denote the row [T(m, n, k) for 0 <= k <= n] and T(m) denote the triangle [T(m, n) for n >= 0]. Then for instance T(2) is the triangle A062253, T(4, 2) is row 2 of A062255 (which is [65, 20, 0]) and T(4, 2, 1) = 20.
		

Crossrefs

A000217(n) = T(n, 1, 0), A001296(n) = T(n, 2, 0), A000292(n) = T(n, 2, 1),
A001297(n) = T(n, 3, 0), A027789(n) = T(n, 3, 1), A000332(n) = T(n, 3, 2),
A001298(n) = T(n, 4, 0), A293610(n) = T(n, 4, 1), A293611(n) = T(n, 4, 2),
A000389(n) = T(n, 4, 3), A112494(n) = T(n, 5, 0), A293612(n) = T(n, 5, 1),
A293613(n) = T(n, 5, 2), A293614(n) = T(n, 5, 3), A000579(n) = T(n, 5, 4),
A144969(n) = T(n, 6, 0), A000580(n) = T(n, 6, 5), A000295(n) = T(1, n, 1),
A000460(n) = T(1, n, 2), A000498(n) = T(1, n, 3), A000505(n) = T(1, n, 4),
A000514(n) = T(1, n, 5), A001243(n) = T(1, n, 6), A001244(n) = T(1, n, 7),
A126646(n) = T(2, n, 0), A007820(n) = T(n, n, 0).

Programs

  • Maple
    A293616 := proc(m, n, k) option remember:
    if m = 0 then m^n elif k < 0 or k > n then 0 elif n = 0 then 1 else
    (k+m)*A293616(m,n-1,k) + (n-k)*A293616(m,n-1,k-1) + A293616(m-1,n,k) fi end:
    for m in [$0..4] do for n in [$0..6] do print(seq(A293616(m, n, k), k=0..n)) od od;
    # Sample uses:
    A001298 := n -> A293616(n, 4, 0): A293614 := n -> A293616(n, 5, 3):
    # Flatten:
    a := proc(n) local w; w := proc(k) local t, s; t := 1; s := 1;
    while t <= k do s := s + 1; t := t + s od; [s - 1, s - t + k] end:
    seq(A293616(n - k, w(k)[1], w(k)[2]), k=0..n) end: seq(a(n), n = 0..11);
  • Mathematica
    GenEulerianRow[0, n_] := Table[If[n==0 && j==0,1,0], {j,0,n}];
    GenEulerianRow[m_, n_] := If[n==0,{1},Join[CoefficientList[x^(-m) (1 - x)^(n+m)
        PolyLog[-n-m, m, x] /. Log[1-x] -> 0, x], {0}]];
    (* Sample use: *)
    A173018Row[n_] := GenEulerianRow[1, n]; Table[A173018Row[n], {n, 0, 6}]

Formula

T(m, n, k) = (k + m)*T(m, n-1, k) + (n - k)*T(m, n-1, k-1) + T(m-1, n, k) with boundary conditions T(0, n, k) = 0^n; T(m, n, k) = 0 if k < 0 or k > n; and T(m, 0, k) = 0^k.
Let h(m, n) = x^(-m)*(1 - x)^(n + m)*PolyLog(-n - m, m, x) and p(m, n) the polynomial given by the expansion of h(m, n) after replacing log(1 - x) by 0. Then T(m, n, k) is the k-th coefficient of p(m, n) for 0 <= k < n.

A048470 a(n) = (n+1)*(2^(n+1) - n)/2.

Original entry on oeis.org

1, 3, 9, 26, 70, 177, 427, 996, 2268, 5075, 11209, 24510, 53170, 114597, 245655, 524168, 1113976, 2359143, 4980565, 10485570, 22019886, 46137113, 96468739, 201326316, 419430100, 872414907, 1811938977, 3758096006, 7784627818
Offset: 0

Views

Author

Keywords

Comments

a(n) = T(0,n) + T(1,n-1) + ... + T(n,0), array T given by A047858.
Sum of the consecutive integers from 2^n-n up to and including 2^n. - J. M. Bergot, Jun 27 2013

Programs

  • Magma
    [(n+1)*(2^(n+1)-n)/2: n in [0..30]]; // Vincenzo Librandi, Sep 23 2011
    
  • PARI
    a(n)=(n+1)*(2<Charles R Greathouse IV, Jun 28 2013

Formula

G.f.: (-1 + 5*x^3 - 7*x^2 + 4*x)/((2*x-1)^2*(x-1)^3). - Maksym Voznyy (voznyy(AT)mail.ru), Aug 13 2009
a(n) = 3^n - Eulerian(n,2) = A000244(n) - A000460(n). - Peter Luschny, May 13 2016

Extensions

Edited by T. D. Noe, Dec 11 2006

A085852 Triangle T(n, k) read by rows; given by [0, 1, 0, 2, 0, 3, 0, 4, ...] DELTA [1, 0, 2, 0, 2, 0, 3, 0, 2, 0, 4, 0, 2, 0, ...] (A000005 interspersed with 0's) where DELTA is Deléham's operator defined in A084938.

Original entry on oeis.org

1, 0, 1, 0, 1, 1, 0, 1, 4, 1, 0, 1, 11, 11, 1, 0, 1, 26, 62, 26, 1, 0, 1, 57, 266, 258, 57, 1, 0, 1, 120, 991, 1792, 903, 120, 1, 0, 1, 247, 3405, 10363, 9483, 2829, 247, 1, 0, 1, 502, 11140, 53818, 80342, 42906, 8212, 502, 1, 0, 1, 1013, 35348, 260996
Offset: 0

Views

Author

N. J. A. Sloane, Aug 16 2003

Keywords

Examples

			Triangle begins:
1,
0, 1,
0, 1, 1,
0, 1, 4, 1,
0, 1, 11, 11, 1,
0, 1, 26, 62, 26, 1,
0, 1, 57, 266, 258, 57, 1,
0, 1, 120, 991, 1792, 903, 120, 1,
0, 1, 247, 3405, 10363, 9483, 2829, 247, 1,
0, 1, 502, 11140, 53818, 80342, 42906, 8212, 502, 1,
...
		

Crossrefs

Cf. A000295 (3rd column), A000460 (4th column), A000498 (5th column).

Programs

  • Mathematica
    m = 13;
    (* DELTA is defined in A084938 *)
    DELTA[LinearRecurrence[{0, 2, 0, -1}, {0, 1, 0, 2}, m], Table[ {DivisorSigma[0, n], 0}, {n, 1, m}] // Flatten, m] // Flatten (* Jean-François Alcover, Feb 19 2020 *)

Extensions

Incorrect comment removed by Philippe Deléham, Sep 25 2015

A095889 Number of permutations of [n] with exactly 3 descents which avoid the pattern 4321.

Original entry on oeis.org

10, 148, 1260, 8160, 44790, 220180, 1001000, 4295168, 17633122, 69921460, 269652100, 1016524352, 3760334958, 13690636212, 49172875520, 174559419680, 613383654170, 2136135472020, 7380351046300, 25319087913760, 86308819112550, 292526411823828, 986294675689560
Offset: 5

Views

Author

Mike Zabrocki, Nov 10 2004

Keywords

Crossrefs

Programs

  • PARI
    Vec(2*x^5*(5 - 36*x + 82*x^2 - 36*x^3 - 87*x^4 + 80*x^5) / ((1 - x)^4*(1 - 2*x)^3*(1 - 3*x)^4) + O(x^30)) \\ Colin Barker, Nov 03 2017

Formula

G.f.: 2*x^5*(5 - 36*x + 82*x^2 - 36*x^3 - 87*x^4 + 80*x^5) / ((1 - x)^4*(1 - 2*x)^3*(1 - 3*x)^4).
a(n) = (n*(27 + 81*2^n - 115*3^n + 3*(27*2^n+2*3^n)*n + (-27+3^n)*n^2)) / 162. - Colin Barker, May 03 2019

A328088 a(n) = Sum_{k=4..n} ( binomial(n,k)*(k-2)*(2^k-2*k-2) ) - (2^n-n-1).

Original entry on oeis.org

1, 94, 683, 3520, 15461, 61826, 232543, 838276, 2930585, 10014406, 33633299, 111448904, 365403853, 1187875594, 3834883271, 12309375244, 39320806145, 125090127950, 396537120379, 1253145232336, 3949433330741, 12416933938834, 38953666980143, 121962851990420, 381179210953321, 1189376848680406, 3705576521235683
Offset: 4

Views

Author

N. J. A. Sloane, Oct 17 2019

Keywords

Crossrefs

For the constant term see A000460.

Programs

  • Maple
    f:= n -> 3^(n-1)*(2*n-6) + 2^(n-1)*(-n^2+n+6) - n - 1:
    map(f, [$4..40]); # Robert Israel, Oct 18 2019
  • PARI
    Vec(x^4*(1 + 80*x - 551*x^2 + 1406*x^3 - 1772*x^4 + 1128*x^5 - 288*x^6) / ((1 - x)^2*(1 - 2*x)^3*(1 - 3*x)^2) + O(x^40)) \\ Colin Barker, Oct 19 2019

Formula

a(n) = 3^(n-1)*(2*n-6) + 2^(n-1)*(-n^2+n+6) - n - 1. - Robert Israel, Oct 18 2019
From Colin Barker, Oct 19 2019: (Start)
G.f.: x^4*(1 + 80*x - 551*x^2 + 1406*x^3 - 1772*x^4 + 1128*x^5 - 288*x^6) / ((1 - x)^2*(1 - 2*x)^3*(1 - 3*x)^2).
a(n) = -1 + 3*2^n - 2*3^n + (1/6)*(-6 + 3*2^n + 4*3^n)*n - 2^(-1+n)*n^2 for n>3.
a(n) = 14*a(n-1) - 82*a(n-2) + 260*a(n-3) - 481*a(n-4) + 518*a(n-5) - 300*a(n-6) + 72*a(n-7) for n>10.
(End)
E.g.f.: x^2/2 + 2*x^3/3 + exp(2*x)*(3 - 2*x^2 + (-3 + x)*cosh(x) + (-1 + 3*x)*sinh(x)). - Stefano Spezia, Oct 19 2019
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