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 10 results.

A182172 Number A(n,k) of standard Young tableaux of n cells and height <= k; square array A(n,k), n>=0, k>=0, read by antidiagonals.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 1, 2, 1, 0, 1, 1, 2, 3, 1, 0, 1, 1, 2, 4, 6, 1, 0, 1, 1, 2, 4, 9, 10, 1, 0, 1, 1, 2, 4, 10, 21, 20, 1, 0, 1, 1, 2, 4, 10, 25, 51, 35, 1, 0, 1, 1, 2, 4, 10, 26, 70, 127, 70, 1, 0, 1, 1, 2, 4, 10, 26, 75, 196, 323, 126, 1, 0, 1, 1, 2, 4, 10, 26, 76, 225, 588, 835, 252, 1, 0
Offset: 0

Views

Author

Alois P. Heinz, Apr 16 2012

Keywords

Comments

Also the number A(n,k) of standard Young tableaux of n cells and <= k columns.
A(n,k) is also the number of n-length words w over a k-ary alphabet {a1,a2,...,ak} such that for every prefix z of w we have #(z,a1) >= #(z,a2) >= ... >= #(z,ak), where #(z,x) counts the letters x in word z. The A(4,4) = 10 words of length 4 over alphabet {a,b,c,d} are: aaaa, aaab, aaba, abaa, aabb, abab, aabc, abac, abca, abcd.

Examples

			A(4,2) = 6, there are 6 standard Young tableaux of 4 cells and height <= 2:
  +------+  +------+  +---------+  +---------+  +---------+  +------------+
  | 1  3 |  | 1  2 |  | 1  3  4 |  | 1  2  4 |  | 1  2  3 |  | 1  2  3  4 |
  | 2  4 |  | 3  4 |  | 2 .-----+  | 3 .-----+  | 4 .-----+  +------------+
  +------+  +------+  +---+        +---+        +---+
Square array A(n,k) begins:
  1,  1,  1,   1,   1,   1,   1,   1,   1, ...
  0,  1,  1,   1,   1,   1,   1,   1,   1, ...
  0,  1,  2,   2,   2,   2,   2,   2,   2, ...
  0,  1,  3,   4,   4,   4,   4,   4,   4, ...
  0,  1,  6,   9,  10,  10,  10,  10,  10, ...
  0,  1, 10,  21,  25,  26,  26,  26,  26, ...
  0,  1, 20,  51,  70,  75,  76,  76,  76, ...
  0,  1, 35, 127, 196, 225, 231, 232, 232, ...
  0,  1, 70, 323, 588, 715, 756, 763, 764, ...
		

Crossrefs

Main diagonal gives A000085.
A(2n,n) gives A293128.

Programs

  • Maple
    h:= proc(l) local n; n:=nops(l); add(i, i=l)! /mul(mul(1+l[i]-j
           +add(`if`(l[k]>=j, 1, 0), k=i+1..n), j=1..l[i]), i=1..n)
        end:
    g:= proc(n, i, l) option remember;
          `if`(n=0, h(l), `if`(i<1, 0, `if`(i=1, h([l[], 1$n]),
            g(n, i-1, l) +`if`(i>n, 0, g(n-i, i, [l[], i])))))
        end:
    A:= (n, k)-> g(n, k, []):
    seq(seq(A(n, d-n), n=0..d), d=0..15);
  • Mathematica
    h[l_List] := Module[{n = Length[l]}, Sum[i, {i, l}]!/Product[Product[1 + l[[i]] - j + Sum[If[l[[k]] >= j, 1, 0], {k, i+1, n}], {j, 1, l[[i]]}], {i, 1, n}]];
    g[n_, i_, l_List] := g[n, i, l] = If[n == 0, h[l], If[i < 1, 0, If[i == 1, h[Join[l, Array[1&, n]]], g [n, i-1, l] + If[i > n, 0, g[n-i, i, Append[l, i]]]]]];
    a[n_, k_] := g[n, k, {}];
    Table[Table[a[n, d-n], {n, 0, d}], {d, 0, 15}] // Flatten (* Jean-François Alcover, Dec 06 2013, translated from Maple *)

Formula

Conjecture: A(n,k) ~ k^n/Pi^(k/2) * (k/n)^(k*(k-1)/4) * Product_{j=1..k} Gamma(j/2). - Vaclav Kotesovec, Sep 12 2013

A240609 Number of n-length words w over a 3-ary alphabet such that w is empty or a prefix z concatenated with letter a_i and i=1 or 0 < #(z,a_{i-1}) >= #(z,a_i), where #(z,a_i) counts the occurrences of the i-th letter in z.

Original entry on oeis.org

1, 1, 2, 5, 13, 35, 94, 254, 688, 1872, 5115, 14038, 38689, 107055, 297336, 828699, 2317098, 6498114, 18273861, 51521238, 145604868, 412407942, 1170507375, 3328570513, 9482518041, 27059673745, 77340925350, 221382318131, 634578781229, 1821388557507
Offset: 0

Views

Author

Alois P. Heinz, Apr 09 2014

Keywords

Examples

			a(3) = 5: 111, 112, 121, 122, 123.
a(4) = 13: 1111, 1112, 1121, 1122, 1123, 1211, 1212, 1213, 1221, 1223, 1231, 1232, 1233.
a(5) = 35: 11111, 11112, 11121, 11122, 11123, 11211, 11212, 11213, 11221, 11222, 11223, 11231, 11232, 11233, 12111, 12112, 12113, 12121, 12122, 12123, 12131, 12132, 12133, 12211, 12212, 12213, 12231, 12233, 12311, 12312, 12313, 12321, 12323, 12331, 12332.
		

Crossrefs

Column k=3 of A240608.

Programs

  • Maple
    a:= proc(n) option remember; `if`(n<3, [1, 1, 2][n+1],
          ((87*n^5-380*n^4-95*n^3+848*n^2-76*n+96) *a(n-1)
          +(n-1)*(29*n^4-117*n^3+228*n^2+404*n-528) *a(n-2)
          -3*(n-1)*(n-2)*(29*n^3-59*n^2-34*n-96) *a(n-3))/
          ((n-2)*(n+4)*(29*n^3-146*n^2+171*n-150)))
        end:
    seq(a(n), n=0..35);
  • Mathematica
    b[n_, k_, l_] := b[n, k, l] = If[n == 0, 1, If[Length[l] < k, b[n - 1, k, Append[l, 1]], 0] + Sum[If[i == 1 || l[[i]] <= l[[i - 1]], b[n - 1, k, ReplacePart[l, i -> l[[i]] + 1]], 0], {i, 1, Length[l]}]];
    a[n_] := b[n, Min[3, n], {}];
    a /@ Range[0, 35] (* Jean-François Alcover, Jan 03 2021, after Alois P. Heinz in A240608 *)

Formula

a(n) ~ 29 * 3^(n+3/2) / (16*sqrt(Pi)*n^(3/2)). - Vaclav Kotesovec, Jul 16 2014

A240610 Number of n-length words w over a 4-ary alphabet such that w is empty or a prefix z concatenated with letter a_i and i=1 or 0 < #(z,a_{i-1}) >= #(z,a_i), where #(z,a_i) counts the occurrences of the i-th letter in z.

Original entry on oeis.org

1, 1, 2, 5, 14, 45, 149, 509, 1756, 6082, 21246, 74125, 260940, 917060, 3251573, 11514563, 41115372, 146687475, 527318119, 1894548198, 6853413645, 24782205276, 90165044683, 327958242274, 1199475359682, 4386106532923, 16118279172044, 59223681674225
Offset: 0

Views

Author

Alois P. Heinz, Apr 09 2014

Keywords

Crossrefs

Column k=4 of A240608.

Formula

a(n) ~ 8465 * 4^n / (18 * Pi * n^3). - Vaclav Kotesovec, Aug 28 2014

A240611 Number of n-length words w over a 5-ary alphabet such that w is empty or a prefix z concatenated with letter a_i and i=1 or 0 < #(z,a_{i-1}) >= #(z,a_i), where #(z,a_i) counts the occurrences of the i-th letter in z.

Original entry on oeis.org

1, 1, 2, 5, 14, 46, 164, 629, 2511, 10284, 42765, 179411, 757518, 3212026, 13672821, 58390509, 250183486, 1075280768, 4636221163, 20051763960, 86995226538, 378588153837, 1652550862097, 7234850625649, 31766225617819, 139871594177849, 617573798910950
Offset: 0

Views

Author

Alois P. Heinz, Apr 09 2014

Keywords

Crossrefs

Column k=5 of A240608.

A240612 Number of n-length words w over a 6-ary alphabet such that w is empty or a prefix z concatenated with letter a_i and i=1 or 0 < #(z,a_{i-1}) >= #(z,a_i), where #(z,a_i) counts the occurrences of the i-th letter in z.

Original entry on oeis.org

1, 1, 2, 5, 14, 46, 165, 650, 2742, 12195, 56388, 267382, 1291017, 6304776, 31043333, 153739806, 764663187, 3817811679, 19117378411, 96034890298, 483633087406, 2442935438558, 12369440072730, 62816259353597, 319763315261222, 1632483727134416, 8354058837330795
Offset: 0

Views

Author

Alois P. Heinz, Apr 09 2014

Keywords

Crossrefs

Column k=6 of A240608.

A240613 Number of n-length words w over a 7-ary alphabet such that w is empty or a prefix z concatenated with letter a_i and i=1 or 0 < #(z,a_{i-1}) >= #(z,a_i), where #(z,a_i) counts the occurrences of the i-th letter in z.

Original entry on oeis.org

1, 1, 2, 5, 14, 46, 165, 651, 2770, 12601, 60686, 305658, 1595454, 8547278, 46685641, 258530476, 1446098060, 8148181066, 46165702543, 262699285827, 1500141404881, 8592741193076, 49353003881425, 284185414898313, 1640366631269049, 9490895165369217
Offset: 0

Views

Author

Alois P. Heinz, Apr 09 2014

Keywords

Crossrefs

Column k=7 of A240608.

A240614 Number of n-length words w over an 8-ary alphabet such that w is empty or a prefix z concatenated with letter a_i and i=1 or 0 < #(z,a_{i-1}) >= #(z,a_i), where #(z,a_i) counts the occurrences of the i-th letter in z.

Original entry on oeis.org

1, 1, 2, 5, 14, 46, 165, 651, 2771, 12637, 61352, 314472, 1691635, 9472308, 54830409, 325818836, 1975978117, 12171736767, 75862916184, 477079866910, 3020725897374, 19228274412487, 122916363687789, 788480233155175, 5073010198556052, 32724394668837491
Offset: 0

Views

Author

Alois P. Heinz, Apr 09 2014

Keywords

Crossrefs

Column k=8 of A240608.

A240615 Number of n-length words w over a 9-ary alphabet such that w is empty or a prefix z concatenated with letter a_i and i=1 or 0 < #(z,a_{i-1}) >= #(z,a_i), where #(z,a_i) counts the occurrences of the i-th letter in z.

Original entry on oeis.org

1, 1, 2, 5, 14, 46, 165, 651, 2771, 12638, 61397, 315507, 1708420, 9693168, 57360909, 352099643, 2229930365, 14494768448, 96229497555, 649761232948, 4446218110646, 30745322129155, 214353097904732, 1504152530715607, 10609439744527674, 75146372454242527
Offset: 0

Views

Author

Alois P. Heinz, Apr 09 2014

Keywords

Crossrefs

Column k=9 of A240608.

A240616 Number of n-length words w over a 10-ary alphabet such that w is empty or a prefix z concatenated with letter a_i and i=1 or 0 < #(z,a_{i-1}) >= #(z,a_i), where #(z,a_i) counts the occurrences of the i-th letter in z.

Original entry on oeis.org

1, 1, 2, 5, 14, 46, 165, 651, 2771, 12638, 61398, 315562, 1709960, 9723253, 57831688, 358445901, 2306799588, 15354546420, 105275618325, 740481162174, 5321875886529, 38940082552276, 289132258826130, 2172495189822333, 16480880960094288, 125993420982428718
Offset: 0

Views

Author

Alois P. Heinz, Apr 09 2014

Keywords

Crossrefs

Column k=10 of A240608.

A240617 Number of n-length words w over an n-ary alphabet such that w is empty or a prefix z concatenated with letter a_i and i=1 or 0 < #(z,a_{i-1}) >= #(z,a_i), where #(z,a_i) counts the occurrences of the i-th letter in z.

Original entry on oeis.org

1, 1, 2, 5, 14, 46, 165, 651, 2771, 12638, 61398, 315563, 1710027, 9725543, 57886132, 359476571, 2323518017, 15597303757, 108522502933, 781283103284, 5810573402452, 44579551962460, 352360829928066, 2865876353091752, 23958937424819348, 205673285003637629
Offset: 0

Views

Author

Alois P. Heinz, Apr 09 2014

Keywords

Examples

			a(0) = 1: the empty word.
a(1) = 1: 1.
a(2) = 2: 11, 12.
a(3) = 5: 111, 112, 121, 122, 123.
a(4) = 14: 1111, 1112, 1121, 1122, 1123, 1211, 1212, 1213, 1221, 1223, 1231, 1232, 1233, 1234.
a(5) = 46: 11111, 11112, 11121, ..., 12343, 12344, 12345.
a(6) = 165: 111111, 111112, 111121, ..., 123454, 123455, 123456.
		

Crossrefs

Main diagonal of A240608.
Showing 1-10 of 10 results.