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 21-27 of 27 results.

A000565 Number of discordant permutations.

Original entry on oeis.org

31, 696, 5823, 29380, 108933, 327840, 848380, 1958004, 4130895, 8107024, 14990889, 26372124, 44470165, 72305160, 113897310, 174496828, 260846703, 381480456, 547057075, 770735316, 1068589557, 1460069392, 1968505152, 2621661540
Offset: 7

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Author

Keywords

References

  • J. Riordan, Discordant permutations, Scripta Math., 20 (1954), 14-23.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Programs

  • Magma
    [243/560*n^7-243/16*n^6+3591/16*n^5-28737/16*n^4+ 82257/10*n^3 - 81931/4*n^2+151931/7*n: n in [7..45]]; // Vincenzo Librandi, Feb 10 2016
  • Maple
    pp := n - >243/560*n^7 - 243/16*n^6 + 3591/16*n^5 - 28737/16*n^4 + 82257/10*n^3 - 81931/4*n^2 + 151931/7*n; seq(pp(n), n=0..30); # Barbara Haas Margolius (margolius(AT)math.csuohio.edu), Feb 17 2001
    A000565:=-(12*z**7-6*z**6-131*z**4+88*z**5-1123*z**2-548*z**3-31-448*z)/(z-1)**8; # conjectured by Simon Plouffe in his 1992 dissertation
  • Mathematica
    LinearRecurrence[{8, -28, 56, -70, 56, -28, 8, -1}, {31, 696, 5823, 29380, 108933, 327840, 848380, 1958004}, 30] (* Jean-François Alcover, Feb 10 2016 *)

Formula

From Barbara Haas Margolius (margolius(AT)math.csuohio.edu), Feb 17 2001: (Start)
G.f.: -x^7(12x^7 - 6x^6 + 88x^5 - 131x^4 - 548x^3 - 1123x^2 - 448x - 31) / ((1 - x)^8).
a(n) = 243/560n^7 - 243/16n^6 + 3591/16n^5 - 28737/16n^4 + 82257/10n^3 - 81931/4n^2 + 151931/7n, for n>6. (End)

Extensions

More terms from Barbara Haas Margolius (margolius(AT)math.csuohio.edu), Feb 17 2001

A000562 Number of discordant permutations.

Original entry on oeis.org

9, 95, 420, 1225, 2834, 5652, 10165, 16940, 26625, 39949, 57722, 80835, 110260, 147050, 192339, 247342, 313355, 391755, 484000, 591629, 716262, 859600, 1023425, 1209600, 1420069, 1656857, 1922070, 2217895, 2546600, 2910534, 3312127, 3753890, 4238415, 4768375, 5346524, 5975697
Offset: 4

Views

Author

Keywords

References

  • J. Riordan, Discordant permutations, Scripta Math., 20 (1954), 14-23.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Programs

  • Magma
    [9] cat [27/8*n^4-135/4*n^3+921/8*n^2-539/4*n: n in [5..45]]; // Vincenzo Librandi, Feb 10 2016
  • Maple
    ff := n->27/8*n^4-135/4*n^3+921/8*n^2-539/4*n; seq(ff(n), n=5..40); # Barbara Haas Margolius (margolius(AT)math.csuohio.edu), Feb 17 2001
    A000562:=(-9-50*z-35*z**2+15*z**3-4*z**4+2*z**5)/(z-1)**5; # conjectured by Simon Plouffe in his 1992 dissertation
  • Mathematica
    Join[{9}, LinearRecurrence[{5, -10, 10, -5, 1}, {95, 420, 1225, 2834, 5652}, 40]] (* Jean-François Alcover, Feb 10 2016 *)

Formula

From Barbara Haas Margolius (margolius(AT)math.csuohio.edu), Feb 17 2001: (Start)
G.f.: -x^4(2x^5 - 4x^4 + 15x^3 - 35x^2 - 50x - 9) / ((1 - x)^5).
a(n) = 27/8n^4 - 135/4n^3 + 921/8n^2 - 539/4n, n>4. (End)

Extensions

More terms from Barbara Haas Margolius (margolius(AT)math.csuohio.edu), Feb 17 2001

A000563 Number of discordant permutations.

Original entry on oeis.org

13, 192, 1085, 3880, 10656, 24626, 50380, 94128, 163943, 270004, 424839, 643568, 944146, 1347606, 1878302, 2564152, 3436881, 4532264, 5890369, 7555800, 9577940, 12011194, 14915232, 18355232, 22402123, 27132828, 32630507, 38984800, 46292070
Offset: 5

Views

Author

Keywords

References

  • J. Riordan, Discordant permutations, Scripta Math., 20 (1954), 14-23.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Programs

  • Magma
    [81/40*n^5-135/4*n^4+1719/8*n^3-2487/4*n^2+3463/5*n: n in [5..45]]; // Vincenzo Librandi, Feb 10 2016
  • Maple
    r := n->81/40*n^5-135/4*n^4+1719/8*n^3-2487/4*n^2+3463/5*n; seq(r(n), n=5..40); # Barbara Haas Margolius (margolius(AT)math.csuohio.edu), Feb 17 2001
    A000563:=-(-13-114*z-128*z**2+10*z**3-6*z**4+8*z**5)/(z-1)**6; # conjectured by Simon Plouffe in his 1992 dissertation
  • Mathematica
    LinearRecurrence[{6, -15, 20, -15, 6, -1}, {13, 192, 1085, 3880, 10656, 24626}, 30] (* Jean-François Alcover, Feb 10 2016 *)

Formula

From Barbara Haas Margolius (margolius(AT)math.csuohio.edu), Feb 17 2001: (Start)
G.f.: -x^5(8x^5 - 6x^4 + 10x^3 - 128x^2 - 114x - 13) / ((1 - x)^6).
a(n) = 81/40n^5 - 135/4n^4 + 1719/8n^3 - 2487/4n^2 + 3463/5n, n>4. (End)

Extensions

More terms from Barbara Haas Margolius (margolius(AT)math.csuohio.edu), Feb 17 2001

A000564 Number of discordant permutations.

Original entry on oeis.org

20, 371, 2588, 11097, 35645, 94457, 218124, 454220, 872648, 1571715, 2684936, 4388567, 6909867, 10536089, 15624200, 22611330, 32025950, 44499779, 60780420, 81744725, 108412889, 141963273, 183747956, 235309016, 298395540
Offset: 6

Views

Author

Keywords

References

  • J. Riordan, Discordant permutations, Scripta Math., 20 (1954), 14-23.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Programs

  • Magma
    [20] cat [81/80*n^6-405/16*n^5+4113/16*n^4-21267/16*n^3+140357/40*n^2 - 7587/2*n: n in [7..45]]; // Vincenzo Librandi, Feb 10 2016
  • Maple
    rr := n - >81/80*n^6 - 405/16*n^5 + 4113/16*n^4 - 21267/16*n^3 + 140357/40*n^2 - 7587/2*n; seq(rr(n), n=7..40); # Barbara Haas Margolius (margolius(AT)math.csuohio.edu), Feb 17 2001
    A000564:=(-20-231*z-411*z**2-72*z**3-29*z**4+36*z**5-4*z**6+2*z**7)/(z-1)**7; # conjectured by Simon Plouffe in his 1992 dissertation
  • Mathematica
    Join[{20}, LinearRecurrence[{7, -21, 35, -35, 21, -7, 1}, {371, 2588, 11097, 35645, 94457, 218124, 454220}, 30]] (* Jean-François Alcover, Feb 10 2016 *)

Formula

From Barbara Haas Margolius (margolius(AT)math.csuohio.edu), Feb 17 2001: (Start)
G.f.: -x^6(2x^7 - 4x^6 + 36x^5 - 29x^4 - 72x^3 - 411x^2 - 231x - 20) / ((1 - x)^7).
a(n) = 81/80n^6 - 405/16n^5 + 4113/16n^4 - 21267/16n^3 + 140357/40n^2 - 7587/2n, n>6. (End)

Extensions

More terms from Barbara Haas Margolius (margolius(AT)math.csuohio.edu), Feb 17 2001

A001926 G.f.: (1+x)^2/[(1-x)^4(1-x-x^2)^3].

Original entry on oeis.org

1, 9, 46, 177, 571, 1632, 4270, 10446, 24244, 53942, 115954, 242240, 494087, 987503, 1939634, 3753007, 7167461, 13532608, 25293964, 46856332, 86110792, 157125052, 284866900, 513470464, 920659517, 1642844485, 2918680214, 5164483453, 9104522495, 15995633440
Offset: 0

Views

Author

Keywords

Comments

From rook polynomials.

References

  • J. Riordan, Discordant permutations, Scripta Math., 20 (1954), 14-23.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Second differences are in A002941.

Programs

  • Maple
    A001926:=-(1+z)**2/(z**2+z-1)**3/(z-1)**4; # conjectured (correctly) by Simon Plouffe in his 1992 dissertation
  • Mathematica
    nn = 30; CoefficientList[Series[(1 + x)^2/((1 - x)^4 (1 - x - x^2)^3), {x, 0, nn}], x] (* T. D. Noe, Aug 17 2012 *)
    LinearRecurrence[{7,-18,17,7,-24,9,9,-6,-1,1},{1,9,46,177,571,1632,4270,10446,24244,53942},30] (* Harvey P. Dale, Apr 30 2022 *)

Extensions

Edited by N. J. A. Sloane, Apr 10 2009

A259454 Triangle T(n,k) (0 <= k <= n) read by rows, arising from the study of rook polynomials.

Original entry on oeis.org

1, 1, 3, 1, 6, 7, 1, 9, 22, 14, 1, 12, 46, 64, 26, 1, 15, 79, 177, 162, 46, 1, 18, 121, 380, 571, 374, 79, 1, 21, 172, 700, 1496, 1632, 809, 133, 1, 24, 232, 1164, 3261, 5116, 4270, 1668, 221, 1, 27, 301, 1799, 6271, 13013, 15754, 10446, 3316, 364
Offset: 0

Views

Author

N. J. A. Sloane, Jun 28 2015

Keywords

Comments

See Riordan 1954 page 18 equation (9). - Michael Somos, Aug 26 2015

Examples

			Triangle T(n,k) begins:
1;
1,  3;
1,  6,  7;
1,  9,  22,   14;
1, 12,  46,   64,   26;
1, 15,  79,  177,  162,   46;
1, 18, 121,  380,  571,  374,   79;
1, 21, 172,  700, 1496, 1632,  809,  133;
1, 24, 232, 1164, 3261, 5116, 4270, 1668, 221;
G.f. = 1 + (1 + 3*t)*u + (1 + 6*t + 7*t^2)*u^2 + ...
		

Crossrefs

Some diagonals: A001924, A001925, A001926.

Programs

  • Maple
    T:= proc(n, k) option remember; `if`(k<0 or k>n, 0,
          T(n-1, k) +2*T(n-1, k-1) +T(n-2, k-1)
         -T(n-3, k-3) +`if`(n=k, 1, 0))
        end:
    seq(seq(T(n, k), k=0..n), n=0..10);  # Alois P. Heinz, Jul 02 2015
  • Mathematica
    T[n_, k_] /; 0 <= k <= n := T[n, k] = T[n-1, k] + 2*T[n-1, k-1] + T[n-2, k - 1] - T[n-3, k-3] + Boole[n == k]; T[, ] = 0; Table[T[n, k], {n, 0, 10}, {k, 0, n}] // Flatten (* Jean-François Alcover, Feb 18 2016 *)
  • PARI
    {T(n, k) = polcoeff( polcoeff( 1 / ((1 - y*x) * (1 - (1 + 2*y)*x - y*x^2 + y^3*x^3)) + x * O(x^n), n), k)}; /* Michael Somos, Aug 26 2015 */

Formula

From Eq. (11) of Riordan (1954): T(n,k) = T(n-1,k) + 2*T(n-1,k-1) + T(n-2,k-1) - T(n-3,k-3) + delta(n,k), where delta(n,k)=1 iff n=k, otherwise 0.
Sum_{n, k} T(n, k) * x^n*y^k = 1 / ((1 - y*x) * (1 - (1 + 2*y)*x - y*x^2 + y^3*x^3)). - Michael Somos, Aug 26 2015

Extensions

More terms from Alois P. Heinz, Jul 02 2015

A094315 Triangle read by rows giving number of circular permutations of n letters such that all letters are displaced by no more than k places from their original position.

Original entry on oeis.org

1, 0, 1, 0, 0, 2, 0, 0, 0, 6, 1, 0, 6, 8, 9, 2, 15, 20, 40, 30, 13, 20, 72, 180, 176, 180, 72, 20, 144, 609, 1106, 1421, 980, 595, 154, 31, 1265, 4960, 9292, 10352, 8326, 4096, 1676, 304, 49
Offset: 0

Views

Author

N. J. A. Sloane, based on a suggestion from Anthony C Robin, Jun 02 2004

Keywords

Comments

The n-th row sums to n!.

Examples

			1;
0, 1;
0, 0, 2;
0, 0, 0, 6;
1, 0, 6, 8, 9;
2, 15, 20, 40, 30, 13;
20, 72, 180, 176, 180, 72, 20;
144, 609, 1106, 1421, 980, 595, 154, 31;
		

References

  • J. Riordan, Discordant permutations, Scripta Math., 20 (1954), 14-23.

Crossrefs

Diagonals give A000183 (which has further references), A000476, A000388, A000380, A000440, etc.
See also A061702.

Formula

Riordan (1954) is devoted to the study of these numbers and gives generating functions (involving the numbers in A061702 as coefficients).
Previous Showing 21-27 of 27 results.