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 13 results. Next

A124577 Define p(alpha) to be the number of H-conjugacy classes where H is a Young subgroup of type alpha of the symmetric group S_n. Then a(n) = sum p(alpha) where |alpha| = n and alpha has at most n parts.

Original entry on oeis.org

1, 1, 6, 39, 356, 4055, 57786, 983535, 19520264, 441967518, 11235798510, 316719689506, 9800860032876, 330230585628437, 12032866998445818, 471416196117401340, 19758835313514076176, 882185444649249777913, 41797472220815112375966, 2094455101139881670407954
Offset: 0

Views

Author

Richard Bayley (r.t.bayley(AT)qmul.ac.uk), Nov 05 2006

Keywords

Comments

p((0,n)) = A000041, p((1,n)) = A000070, p((2,n)) = A093695;
Also main diagonal of A209664. - Wouter Meeussen, Mar 11 2012
Number of partitions of n into n sorts of parts. a(2) = 6: [2a], [2b], [1a,1a], [1a,1b], [1b,1a], [1b,1b]. - Alois P. Heinz, Sep 08 2014

Examples

			E.g p((2,1)) = # H-conjugacy classes of S_3 where H = Yng((2,1)) isom S_2 times S_1 . Then a(3) = p((3)) + p((2,1)) + p((2,0,1)) + p((1,2)) + p((1,1,1))+ p((1,0,2)+ p((0,2,1)) + p((0,1,2)) + p((0,0,3)) = 3+4+4+4+6+4+3+4+4+3 = 39.
		

Crossrefs

Programs

  • Maple
    b:= proc(n, i, k) option remember; `if`(n=0, 1, `if`(i<1, 0,
          b(n, i-1, k) +`if`(i>n, 0, k*b(n-i, i, k))))
        end:
    a:= n-> b(n$3):
    seq(a(n), n=0..20);  # Alois P. Heinz, Sep 08 2014
  • Mathematica
    p[n_Integer, v_] := Sum[Subscript[x, j]^n, {j, v}];
    p[par_List, v_] := Times @@ (p[#, v] & /@ par);
    Tr /@ Table[(p[#, l] & /@ IntegerPartitions[l]) /. Subscript[x, ] -> 1, {l, 19}] (* _Wouter Meeussen, Mar 11 2012 *)
    b[n_, i_, k_] := b[n, i, k] = If[n == 0, 1, If[i < 1, 0, b[n, i - 1, k] + If[i > n, 0, k*b[n - i, i, k]]]]; a[n_] := b[n, n, n]; Table[a[n], {n, 0, 20}] (* Jean-François Alcover, Aug 29 2016, after Alois P. Heinz *)
  • PARI
    {a(n)=polcoeff(1/prod(k=1,n,1-n*x^k +x*O(x^n)),n)} \\ Paul D. Hanna, Nov 26 2009

Formula

Let x = x_1x_2x_3... and x^alpha = x_1^(alpha_1)x_2^(alpha_2)x_3^(alpha_3).... Let Phi = set of all primitive necklaces. If b is a primitive necklace then C(b) = Content(b) = (beta_1, beta_2,beta_3,.....) where beta_i = the number of times i occurs in b. For example if b=[11233] then C(b) = (2,1,2). To generate the p(alpha) we do the following. sum_alpha p(alpha)x^alpha = prod_(b in Phi) prod_(k = 1)^infinity 1/(1- x^(c(b) times k )) = prod_(b in Phi) prod_(k = 1)^infinity (1+ x^(k times C(b)) + x^(2k times C(b)) + x^(3k times C(b)) + ....)
From Paul D. Hanna, Nov 26 2009: (Start)
a(n) = [x^n] Product_{k>=1} 1/(1 - n*x^k) for n>0.
a(n) = Sum_{k=1..n} A008284(n,k)*n^k, where A008284(n,k) = number of partitions of n in which the greatest part is k, 1<=k<=n. (End)
a(n) ~ n^n * (1 + 1/n + 2/n^2 + 3/n^3 + 5/n^4 + 7/n^5 + 11/n^6 + 15/n^7 + 22/n^8 + 30/n^9 + 42/n^10), where the coefficients are A000041(k)/n^k. - Vaclav Kotesovec, Mar 19 2015

Extensions

Extended with formula by Paul D. Hanna, Nov 26 2009
a(0) inserted and more terms from Alois P. Heinz, Sep 08 2014

A340103 a(n) = [x^n] Product_{k>=1} (1 + n^(k-1)*x^k).

Original entry on oeis.org

1, 1, 2, 12, 80, 875, 10584, 170471, 2949120, 63772920, 1441000000, 38818444632, 1089573617664, 35185728919614, 1175820172477440, 44425722744140625, 1722925924631969792, 74364737115532234518, 3291298649632850485248, 159785357022861166517580, 7932051456000000000000000
Offset: 0

Views

Author

Ilya Gutkovskiy, Apr 24 2021

Keywords

Crossrefs

Programs

  • Mathematica
    Table[SeriesCoefficient[Product[(1 + n^(k - 1) x^k), {k, 1, n}], {x, 0, n}], {n, 0, 20}]
    Unprotect[Power]; 0^0 = 1; Table[Sum[Length[Select[IntegerPartitions[n, {k}], UnsameQ @@ # &]] n^(n - k), {k, 0, Floor[(Sqrt[8 n + 1] - 1)/2]}], {n, 0, 20}]
    Join[{1}, Table[SeriesCoefficient[n*QPochhammer[-1/n, n*x]/(n+1), {x, 0, n}], {n, 1, 20}]] (* Vaclav Kotesovec, May 09 2021 *)

Formula

a(n) = Sum_{k=0..A003056(n)} q(n,k) * n^(n-k), where q(n,k) is the number of partitions of n into k distinct parts.
a(n) ~ c * n^(n-1), where c = BesselI(1,2) = A096789 = 1.590636854637329... - Vaclav Kotesovec, May 09 2021

A261569 Expansion of Product_{k>=1} (1 + 5*x^k).

Original entry on oeis.org

1, 5, 5, 30, 30, 55, 180, 205, 330, 480, 1230, 1380, 2255, 3030, 4530, 8555, 10680, 15330, 21330, 29730, 39480, 67380, 81505, 116280, 153030, 210930, 270805, 370080, 534330, 675480, 900480, 1180380, 1544130, 1997280, 2597280, 3304805, 4581180, 5653080
Offset: 0

Views

Author

Vaclav Kotesovec, Aug 24 2015

Keywords

Comments

In general, for a fixed integer m > 0, if g.f. = Product_{k>=1} (1 + m*x^k) then a(n) ~ c^(1/4) * exp(2*sqrt(c*n)) / (2*sqrt((m+1)*Pi)*n^(3/4)), where c = Pi^2/6 + log(m)^2/2 + polylog(2, -1/m) = -polylog(2, -m). - Vaclav Kotesovec, Jan 04 2016

Crossrefs

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(i*(i+1)/2n, 0, 5*b(n-i, i-1))))
        end:
    a:= n-> b(n$2):
    seq(a(n), n=0..60);  # Alois P. Heinz, Aug 24 2015
  • Mathematica
    nmax = 40; CoefficientList[Series[Product[1 + 5*x^k, {k, 1, nmax}], {x, 0, nmax}], x]
    nmax = 40; CoefficientList[Series[Exp[Sum[(-1)^(k+1)*5^k/k*x^k/(1-x^k), {k, 1, nmax}]], {x, 0, nmax}], x] (* Vaclav Kotesovec, Aug 25 2015 *)
    (QPochhammer[-5, x]/6 + O[x]^58)[[3]] (* Vladimir Reshetnikov, Nov 20 2015 *)

Formula

a(n) ~ c^(1/4) * exp(2*sqrt(c*n)) / (2*sqrt(6*Pi)*n^(3/4)), where c = Pi^2/6 + log(5)^2/2 + polylog(2, -1/5) = 2.74927912606080829002558751537626864449... . - Vaclav Kotesovec, Jan 04 2016
G.f.: Sum_{i>=0} 5^i*x^(i*(i+1)/2)/Product_{j=1..i} (1 - x^j). - Ilya Gutkovskiy, Apr 12 2018

A286957 Square array A(n,k), n>=0, k>=0, read by antidiagonals, where column k is the expansion of Product_{j>=1} (1 + k*x^j).

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 2, 1, 0, 1, 3, 2, 2, 0, 1, 4, 3, 6, 2, 0, 1, 5, 4, 12, 6, 3, 0, 1, 6, 5, 20, 12, 10, 4, 0, 1, 7, 6, 30, 20, 21, 18, 5, 0, 1, 8, 7, 42, 30, 36, 48, 22, 6, 0, 1, 9, 8, 56, 42, 55, 100, 57, 30, 8, 0, 1, 10, 9, 72, 56, 78, 180, 116, 84, 42, 10, 0, 1, 11, 10, 90, 72, 105, 294, 205, 180, 120, 66, 12, 0
Offset: 0

Views

Author

Ilya Gutkovskiy, May 17 2017

Keywords

Comments

A(n,k) is the number of partitions of n into distinct parts of k sorts: the parts are unordered, but not the sorts.

Examples

			Square array begins:
1,  1,   1,   1,   1,   1,  ...
0,  1,   2,   3,   4,   5,  ...
0,  1,   2,   3,   4,   5,  ...
0,  2,   6,  12,  20,  30,  ...
0,  2,   6,  12,  20,  30,  ...
0,  3,  10,  21,  36,  55,  ...
		

Crossrefs

Columns k=0-5 give: A000007, A000009, A032302, A032308, A261568, A261569.
Main diagonal gives A291698.
Cf. A246935.

Programs

  • Mathematica
    Table[Function[k, SeriesCoefficient[Product[(1 + k x^i), {i, 1, Infinity}], {x, 0, n}]][j - n], {j, 0, 12}, {n, 0, j}] // Flatten
    Table[Function[k, SeriesCoefficient[QPochhammer[-k, x]/(1 + k), {x, 0, n}]][j - n], {j, 0, 12}, {n, 0, j}] // Flatten

Formula

G.f. of column k: Product_{j>=1} (1 + k*x^j).

A292305 a(n) = [x^n] Product_{k>=1} (1 + n^k*x^k).

Original entry on oeis.org

1, 1, 4, 54, 512, 9375, 186624, 4117715, 100663296, 3099363912, 100000000000, 3423740047332, 133741506723840, 5451751918660554, 244464150162276352, 11823135040283203125, 590295810358705651712, 31435129951680797038726, 1809934771463640728469504
Offset: 0

Views

Author

Vaclav Kotesovec, Sep 14 2017

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 20; Table[SeriesCoefficient[Product[(1+n^k*x^k), {k, 1, n}], {x, 0, n}], {n, 0, nmax}]
    Flatten[{1, Table[n^n*PartitionsQ[n], {n, 1, 20}]}]

Formula

a(n) = n^n * A000009(n).
a(n) ~ exp(Pi*sqrt(n/3)) * n^(n-3/4) / (4*3^(1/4)).

A292304 a(n) = [x^n] Product_{k>=1} (1 + n^2*x^k).

Original entry on oeis.org

1, 1, 4, 90, 272, 1275, 49284, 124901, 536640, 1620648, 104040100, 223290012, 880969104, 2485978170, 7454471332, 592164776475, 1138401673472, 4109108002310, 10877348160900, 30962024560494, 72270337440400, 7523649856001916, 13202150810778116, 44577985082575400
Offset: 0

Views

Author

Vaclav Kotesovec, Sep 14 2017

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 30; Table[SeriesCoefficient[Product[(1+n^2*x^k), {k, 1, n}], {x, 0, n}], {n, 0, nmax}]
    Table[SeriesCoefficient[QPochhammer[-n^2, x, 1 + n]/(1 + n^2), {x, 0, n}], {n, 0, 30}]

Formula

Conjecture: a(n) ~ exp(2*sqrt((Pi^2/6 + 2*log(n)^2)*n)) * (Pi^2/6 + 2*log(n)^2)^(1/4) / (2 * sqrt(Pi) * n^(7/4)).

A298987 a(n) = [x^n] Product_{k>=1} (1 + n*x^k)^k.

Original entry on oeis.org

1, 1, 4, 27, 80, 400, 1908, 6223, 31296, 116478, 450100, 1828915, 7360848, 26906828, 95776772, 403908975, 1421758720, 5072014447, 18481180644, 68350964211, 246180936400, 827642046294, 2958748580084, 10294629775620, 36607347335232, 120800714172500, 407951731319860, 1405943613730899
Offset: 0

Views

Author

Ilya Gutkovskiy, Jan 31 2018

Keywords

Crossrefs

Programs

  • Mathematica
    Table[SeriesCoefficient[Product[(1 + n x^k)^k, {k, 1, n}], {x, 0, n}], {n, 0, 27}]

A292132 Main diagonal of A292131.

Original entry on oeis.org

1, -1, -2, 6, 12, 45, -150, -203, -840, -1872, 6390, 8580, 30084, 69108, 165802, -494565, -514320, -1997296, -4202298, -10175526, -18908420, 49930440, 54032770, 190735688, 405256872, 948210600, 1751280726, 3624555168, -7676955468, -6724059944, -26741354430
Offset: 0

Views

Author

Seiichi Manyama, Sep 09 2017

Keywords

Crossrefs

Programs

  • PARI
    {a(n) = polcoeff(prod(k=1, n, 1-n*x^k+x*O(x^n)), n)}

Formula

a(n) = [x^n] Product_{k=1..n} (1 - n*x^k).

A292134 Main diagonal of A292133.

Original entry on oeis.org

1, -1, 2, -21, 220, -2705, 40926, -733537, 15124216, -352606050, 9174382490, -263533561852, 8283376452948, -282795708021411, 10420847619031710, -412243715452039440, 17425722339237083120, -783844576340696848341, 37384875796116662077194
Offset: 0

Views

Author

Seiichi Manyama, Sep 09 2017

Keywords

Crossrefs

Programs

  • PARI
    {a(n) = polcoeff(1/prod(k=1, n, 1+n*x^k+x*O(x^n)), n)}

Formula

a(n) = [x^n] Product_{k>=1} 1/(1 + n*x^k).
a(n) ~ (-1)^n * n^n * (1 - 1/n + 2/n^2 - 3/n^3 + 5/n^4 - 7/n^5 + 11/n^6 - 15/n^7 + 22/n^8 - 30/n^9 + 42/n^10 - ...), for coefficients, see A000041. - Vaclav Kotesovec, Aug 21 2018

A303188 a(n) = [x^n] Product_{k=1..n} (1 + (n - k + 1)*x^k).

Original entry on oeis.org

1, 1, 1, 7, 9, 23, 148, 221, 526, 1040, 6767, 9664, 23456, 43943, 91363, 499028, 736410, 1650395, 3107540, 6210372, 10819270, 57864166, 80663444, 179915133, 324882691, 640398244, 1087149284, 2039724322, 9121580902, 12913282685, 27250167385, 48645989650, 92634730208, 156124357449
Offset: 0

Views

Author

Ilya Gutkovskiy, Apr 19 2018

Keywords

Examples

			a(0) = 1;
a(1) = [x^1] (1 + x) = 1;
a(2) = [x^2] (1 + 2*x)*(1 + x^2) = 1;
a(3) = [x^3] (1 + 3*x)*(1 + 2*x^2)*(1 + x^3) = 7;
a(4) = [x^4] (1 + 4*x)*(1 + 3*x^2)*(1 + 2*x^3)*(1 + x^4) = 9;
a(5) = [x^5] (1 + 5*x)*(1 + 4*x^2)*(1 + 3*x^3)*(1 + 2*x^4)*(1 + x^5) = 23, etc.
...
The table of coefficients of x^k in expansion of Product_{k=1..n} (1 + (n - k + 1)*x^k) begins:
n = 0: (1), 0,  0,   0,   0,   0,  ...
n = 1:  1, (1), 0,   0,   0,   0,  ...
n = 2:  1,  2, (1),  2,   0,   0   ...
n = 3:  1,  3,  2,  (7),  3,   2,  ...
n = 4:  1,  4,  3,  14,  (9), 10,  ...
n = 5:  1,  5,  4,  23,  17, (23), ...
		

Crossrefs

Programs

  • Mathematica
    Table[SeriesCoefficient[Product[(1 + (n - k + 1) x^k), {k, 1, n}], {x, 0, n}], {n, 0, 33}]
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