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 1-10 of 25 results. Next

A158423 Number of permutations of 1..n containing the relative rank sequence { 23145 } at any spacing.

Original entry on oeis.org

1, 26, 459, 7034, 101953, 1454402, 20863742, 304906732, 4578822750, 71092815624, 1146499731400, 19270199314388, 338394827020511, 6218127006568582, 119650035623211443, 2410982527835022898, 50846926185692443237, 1121251553648267523078, 25820703260713964268656, 620088145746453017943268
Offset: 5

Views

Author

R. H. Hardin, Mar 18 2009

Keywords

Comments

Same series for 43521 12534 54132 35421 31245 12453 54213 43512 23154 21534 45132 35412 31254 21453 45213.

Crossrefs

Formula

Conjecture: a(n) + A116485(n) = n!. - Benedict W. J. Irwin, Mar 15 2016
Proof: see A116485.

Extensions

a(17) onwards from A116485, by Martin Fuller, Aug 26 2023

A047889 Number of permutations in S_n with longest increasing subsequence of length <= 4.

Original entry on oeis.org

1, 1, 2, 6, 24, 119, 694, 4582, 33324, 261808, 2190688, 19318688, 178108704, 1705985883, 16891621166, 172188608886, 1801013405436, 19274897768196, 210573149141896, 2343553478425816, 26525044132374656, 304856947930144656
Offset: 0

Views

Author

Eric Rains (rains(AT)caltech.edu), N. J. A. Sloane

Keywords

Comments

Or, number of permutations in S_n that avoid the pattern 12345, - N. J. A. Sloane, Mar 19 2015
Also, the dimension of the space of SL(4)-invariants in V^m ⊗ (V^*)^m, where V is the standard 4-dimensional representation of SL(4) and V^* its dual. - Alec Mihailovs (alec(AT)mihailovs.com), Aug 14 2005

Examples

			G.f. = 1 + x + 2*x^2 + 6*x^3 + 24*x^4 + 119*x^5 + 694*x^6 + 4582*x^7 + ...
		

Crossrefs

A column of A047888.
Column k=4 of A214015.
Representatives for the 16 Wilf-equivalence patterns of length 5 are given in A116485, A047889, and A256195-A256208. - N. J. A. Sloane, Mar 19 2015

Programs

  • Maple
    A:=rsolve({a(0) = 1, a(1) = 1, (n^3 + 16*n^2 + 85*n + 150)*a(n + 2) = (20*n^3 + 182*n^2 + 510*n + 428)*a(n + 1) - (64*n^3 + 256*n^2 + 320*n +128)*a(n)}, a(n), makeproc): # Alec Mihailovs (alec(AT)mihailovs.com), Aug 14 2005
  • Mathematica
    Flatten[{1,RecurrenceTable[{64*(-1+n)^2*n*a[-2+n]-2*(-12 + 11*n + 31*n^2 + 10*n^3)*a[-1+n] + (3+n)^2*(4+n)*a[n]==0,a[1]==1,a[2]==2},a,{n,20}]}] (* Vaclav Kotesovec, Sep 10 2014 *)
  • PARI
    {a(n) = my(v); if( n<2, n>=0, v = vector(n+1, k, 1); for(k=2, n, v[k+1] = ((20*k^3 + 62*k^2 + 22*k - 24) * v[k] - 64*k*(k-1)^2 * v[k-1]) / ((k+3)^2 * (k+4))); v[n+1])}; /* Michael Somos, Apr 19 2015 */

Formula

a(0)=1, a(1)=1, (n^3 + 16*n^2 + 85*n + 150)*a(n+2) = (20*n^3 + 182*n^2 + 510*n + 428)*a(n+1) - (64*n^3 + 256*n^2 + 320*n + 128)*a(n). - Alec Mihailovs (alec(AT)mihailovs.com), Aug 14 2005
a(n) = (64*(n+1)*(2*n^3 + 21*n^2 + 76*n + 89)*A002895(n) -(8*n^4 + 104*n^3 + 526*n^2 + 1098*n + 776) *A002895(n+1)) / (3*(n+2)^3*(n+3)^3*(n+4)). - Mark van Hoeij, Jun 02 2010
a(n) ~ 3 * 2^(4*n + 9) / (n^(15/2) * Pi^(3/2)). - Vaclav Kotesovec, Sep 10 2014

Extensions

More terms from Naohiro Nomoto, Mar 01 2002
Edited by N. J. A. Sloane, Aug 23 2008 at the suggestion of R. J. Mathar

A099952 Number of Wilf classes in S_n.

Original entry on oeis.org

1, 1, 1, 3, 16, 91, 595
Offset: 1

Views

Author

N. J. A. Sloane, Nov 12 2004

Keywords

References

  • Z. Stankova and J. West, A new class of Wilf-equivalent permutations, J. Algeb. Combin., 15 (2002), 271-290.

Crossrefs

Representatives for the three Wilf classes in S_4 are A005802, A022558, A061552. - N. J. A. Sloane, Mar 15 2015
Representatives for the 16 Wilf-equivalence patterns of length 5 are given in A116485, A047889, and A256195-A256208. - N. J. A. Sloane, Mar 19 2015

A256195 Number of permutations in S_n that avoid the pattern 25314.

Original entry on oeis.org

1, 1, 2, 6, 24, 119, 694, 4578, 33184, 258757, 2136978, 18478134, 165857600, 1535336290, 14584260700, 141603589300, 1400942032152, 14087464765300, 143689133196008, 1484090443264936, 15499968503875136, 163501005435759505, 1740170514634463426, 18671118911254798454
Offset: 0

Views

Author

N. J. A. Sloane, Mar 19 2015

Keywords

Crossrefs

Representatives for the 16 Wilf-equivalence patterns of length 5 are given in A116485, A047889, and A256195-A256208.
Cf. A099952.

Programs

  • Mathematica
    avoid[n_, pat_] := Module[{p1 = pat[[1]], p2 = pat[[2]], p3 = pat[[3]], p4 = pat[[4]], p5 = pat[[5]], lseq = {}, i, p,
        lpat = Subsets[(n + 1) - Range[n], {Length[pat]}],
        psn = Permutations[Range[n]]},
       For[i = 1, i <= Length[lpat], i++,
        p = lpat[[i]];
        AppendTo[lseq, Select[psn, MemberQ[#, {_, p[[p1]], _, p[[p2]], _, p[[p3]], _, p[[p4]], _, p[[p5]], _}, {0}] &]];
        ]; n! - Length[Union[Flatten[lseq, 1]]]];
    Table[avoid[n, {2, 5, 3, 1, 4}], {n, 0, 8}]  (* Robert Price, Mar 27 2020 *)

Extensions

a(14)-a(16) from Bert Dobbelaere, Mar 18 2021
More terms from Anthony Guttmann, Sep 29 2021

A256208 Number of permutations in S_n that avoid the pattern 52341.

Original entry on oeis.org

1, 1, 2, 6, 24, 119, 694, 4582, 33325, 261863, 2192390, 19358590, 178904675, 1720317763, 17132629082, 176055309619, 1861037944163, 20185165186517, 224150069984572, 2543698932578158, 29451619807433107, 347417296695040510, 4170088041714300134, 50874753262007210667
Offset: 0

Views

Author

N. J. A. Sloane, Mar 19 2015

Keywords

Crossrefs

Representatives for the 16 Wilf-equivalence patterns of length 5 are given in A116485, A047889, and A256195-A256208.
Cf. A099952.

Programs

  • Mathematica
    avoid[n_, pat_] := Module[{p1 = pat[[1]], p2 = pat[[2]], p3 = pat[[3]], p4 = pat[[4]], p5 = pat[[5]], lseq = {}, i, p,
        lpat = Subsets[(n + 1) - Range[n], {Length[pat]}],
        psn = Permutations[Range[n]]},
       For[i = 1, i <= Length[lpat], i++,
        p = lpat[[i]];
        AppendTo[lseq, Select[psn, MemberQ[#, {_, p[[p1]], _, p[[p2]], _, p[[p3]], _, p[[p4]], _, p[[p5]], _}, {0}] &]];
        ]; n! - Length[Union[Flatten[lseq, 1]]]];
    Table[avoid[n, {5, 2, 3, 4, 1}], {n, 0, 8}]  (* Robert Price, Mar 27 2020 *)

Extensions

More terms from Anthony Guttmann, Sep 29 2021

A354511 Number of SAWs crossing a square domain of the hexagonal lattice.

Original entry on oeis.org

2, 14, 264, 21512, 5663596, 6478476233, 23432328776346, 365121393771314359, 18039965927005597824652, 3847346539490622663060402802, 2604549807872636495439504536518768, 7613280873970130888072912524910312775000, 70659728324509466176595292882340210105184200002
Offset: 1

Views

Author

Vaclav Kotesovec, Aug 16 2022

Keywords

Crossrefs

A356610 Number of SAWs crossing a rhomboidal domain of the hexagonal lattice.

Original entry on oeis.org

2, 14, 316, 25092, 7374480, 8029311942, 32223151155864, 476605408516689238, 26016526700583361056456, 5246595079903462547245876694, 3911053741699230141571030313824664, 10780907768757190963361134040036893772360, 109919900687141309301630828947780890728732496678
Offset: 1

Views

Author

Vaclav Kotesovec, following a suggestion from Anthony Guttmann, Aug 16 2022

Keywords

Crossrefs

A356616 Number of SAPs crossing a triangular domain of the hexagonal lattice and including top vertex.

Original entry on oeis.org

1, 1, 4, 36, 666, 24696, 1808820, 259300148, 72369408510, 39205936157880, 41152969216872016, 83592236529606631688, 328284931491454739745904, 2490876950205850778116435156, 36494758452603010620499864088198, 1032033208911845667821292289616451218
Offset: 1

Views

Author

Vaclav Kotesovec, following a suggestion from Anthony Guttmann, Aug 16 2022

Keywords

Crossrefs

A256200 Number of permutations in S_n that avoid the pattern 42351.

Original entry on oeis.org

1, 1, 2, 6, 24, 119, 694, 4580, 33252, 260204, 2161930, 18861307, 171341565, 1610345257, 15579644765, 154541844196, 1566713947713, 16190122718865, 170171678529883, 1816001425551270, 19646035298044543, 215179180467834605, 2383465957654163227, 26673704385975326866
Offset: 0

Views

Author

N. J. A. Sloane, Mar 19 2015

Keywords

Crossrefs

Representatives for the 16 Wilf-equivalence patterns of length 5 are given in A116485, A047889, and A256195-A256208.

Programs

  • Mathematica
    avoid[n_, pat_] := Module[{p1 = pat[[1]], p2 = pat[[2]], p3 = pat[[3]], p4 = pat[[4]], p5 = pat[[5]], lseq = {}, i, p,
        lpat = Subsets[(n + 1) - Range[n], {Length[pat]}],
        psn = Permutations[Range[n]]},
       For[i = 1, i <= Length[lpat], i++,
        p = lpat[[i]];
        AppendTo[lseq, Select[psn, MemberQ[#, {_, p[[p1]], _, p[[p2]], _, p[[p3]], _, p[[p4]], _, p[[p5]], _}, {0}] &]];
        ]; n! - Length[Union[Flatten[lseq, 1]]]];
    Table[avoid[n, {4, 2, 3, 5, 1}], {n, 0, 8}]  (* Robert Price, Mar 27 2020 *)

Formula

a(n) = n! - A158434(n). - Andrew Howroyd, May 18 2020

Extensions

a(14)-a(15) added by Andrew Howroyd, May 18 2020
More terms from Anthony Guttmann, Sep 29 2021

A256196 Number of permutations in S_n that avoid the pattern 31524.

Original entry on oeis.org

1, 1, 2, 6, 24, 119, 694, 4579, 33216, 259401, 2147525, 18632512, 167969934, 1563027614, 14937175825, 146016423713, 1455402205257, 14753501614541, 151783381341695, 1582029822426003, 16681492660789425, 177726496203056670, 1911230701872865231, 20726637978574528119
Offset: 0

Views

Author

N. J. A. Sloane, Mar 19 2015

Keywords

Crossrefs

Representatives for the 16 Wilf-equivalence patterns of length 5 are given in A116485, A047889, and A256195-A256208.
Cf. A099952.

Programs

  • Mathematica
    avoid[n_, pat_] := Module[{p1 = pat[[1]], p2 = pat[[2]], p3 = pat[[3]], p4 = pat[[4]], p5 = pat[[5]], lseq = {}, i, p,
        lpat = Subsets[(n + 1) - Range[n], {Length[pat]}],
        psn = Permutations[Range[n]]},
       For[i = 1, i <= Length[lpat], i++,
        p = lpat[[i]];
        AppendTo[lseq, Select[psn, MemberQ[#, {_, p[[p1]], _, p[[p2]], _, p[[p3]], _, p[[p4]], _, p[[p5]], _}, {0}] &]];
        ]; n! - Length[Union[Flatten[lseq, 1]]]];
    Table[avoid[n, {3, 1, 5, 2, 4}], {n, 0, 8}]  (* Robert Price, Mar 27 2020 *)

Extensions

a(14)-a(16) from Bert Dobbelaere, Mar 18 2021
More terms from Anthony Guttmann, Sep 29 2021
Showing 1-10 of 25 results. Next