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 21-30 of 31 results. Next

A323587 Number of strict (distinct parts) plane partitions of n with relatively prime parts.

Original entry on oeis.org

1, 1, 0, 2, 2, 4, 6, 10, 12, 18, 30, 40, 48, 74, 92, 142, 172, 242, 294, 412, 490, 722, 854, 1164, 1396, 1880, 2260, 2976, 3748, 4764, 5792, 7472, 9082, 11488, 14012, 17522, 21830, 26896, 32820, 40536, 49488, 60636, 73626, 89962, 108854, 134240, 160952, 195858
Offset: 0

Views

Author

Gus Wiseman, Jan 20 2019

Keywords

Examples

			The a(9) = 18 plane partitions:
  81   72   621   54   531   432
.
  8   7   61   62   5   51   53   42   43
  1   2   2    1    4   3    1    3    2
.
  6   5   4
  2   3   3
  1   1   2
		

Crossrefs

Cf. A000219, A000837, A003293, A006951, A026007, A100883, A117433 (strict plane partitions), A300275 (plane partitions with relatively prime parts), A303546, A320802, A323584, A323585.

Programs

  • Mathematica
    primeMS[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
    facs[n_]:=If[n<=1,{{}},Join@@Table[Map[Prepend[#,d]&,Select[facs[n/d],Min@@#>=d&]],{d,Rest[Divisors[n]]}]];
    ptnplane[n_]:=Union[Map[Reverse@*primeMS,Join@@Permutations/@facs[n],{2}]];
    Table[Sum[Length[Select[ptnplane[Times@@Prime/@y],And[And@@GreaterEqual@@@#,And@@(GreaterEqual@@@Transpose[PadRight[#]])]&]],{y,Select[IntegerPartitions[n],UnsameQ@@#&&GCD@@#==1&]}],{n,30}]

Formula

Moebius transform of A117433.

A232439 Number T(n,k) of standard Young tableaux with n cells and major index k; triangle T(n,k), n>=0, 0<=k<=n*(n-1)/2, read by rows.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 1, 1, 1, 1, 2, 3, 4, 4, 4, 3, 2, 1, 1, 1, 1, 2, 4, 5, 7, 9, 9, 9, 9, 7, 5, 4, 2, 1, 1, 1, 1, 2, 4, 6, 9, 13, 16, 19, 22, 23, 23, 22, 19, 16, 13, 9, 6, 4, 2, 1, 1, 1, 1, 2, 4, 7, 10, 16, 22, 30, 37, 46, 52, 60, 62, 64, 62
Offset: 0

Views

Author

Joerg Arndt and Alois P. Heinz, Feb 23 2014

Keywords

Comments

Rows are symmetric.
The row beginnings converge to A003293.
T(n,k) is also the number of ballot sequences of length n with k the sum of positions of all ascents, see example.

Examples

			For n=4 the 10 tableaux sorted by major index (sum of descent set) are:
:[1 2 3 4]:[1 3 4]:[1 2] [1 2 4]:[1 4] [1 2 3]:[1 3] [1 3]:[1 2]:[1]:
:         :[2]    :[3 4] [3]    :[2]   [4]    :[2]   [2 4]:[3]  :[2]:
:         :       :             :[3]          :[4]        :[4]  :[3]:
:         :       :             :             :           :     :[4]:
: ---0--- : --1-- : -----2----- : -----3----- : ----4---- : -5- : 6 :
Triangle T(n,k) begins:
1;
1;
1, 1;
1, 1, 1, 1;
1, 1, 2, 2, 2, 1,  1;
1, 1, 2, 3, 4, 4,  4,  3,  2,  1,  1;
1, 1, 2, 4, 5, 7,  9,  9,  9,  9,  7,  5,  4,  2,  1,  1;
1, 1, 2, 4, 6, 9, 13, 16, 19, 22, 23, 23, 22, 19, 16, 13, 9, 6, 4, 2, 1, 1;
The 10 ballot sequences of length 4 are:
##   [ ballot seq] ascent positions  sum
01:  [ 1 1 1 1 ]   (none)            0
02:  [ 1 1 1 2 ]   3                 3
03:  [ 1 1 2 1 ]   2                 2
04:  [ 1 1 2 2 ]   2                 2
05:  [ 1 1 2 3 ]   2 + 3             5
06:  [ 1 2 1 1 ]   1                 1
07:  [ 1 2 1 2 ]   1 + 3             4
08:  [ 1 2 1 3 ]   1 + 3             4
09:  [ 1 2 3 1 ]   1 + 2             3
10:  [ 1 2 3 4 ]   1 + 2 + 3         6
The numbers 2, 3, and 4 appear twice, all others once, so the row four is  1, 1, 2, 2, 2, 1, 1.
		

Crossrefs

Row sums give A000085.

Programs

  • Maple
    b:= proc(l, i) option remember; `if`(l=[], 1, expand(add(
          `if`(l[j]>`if`(j=1, 0, l[j-1]), `if`(j=1 and l[j]=1,
           b(subsop(1=NULL, l), j-1), b(subsop(j=l[j]-1, l), j))*
           x^`if`(j>i, add(t, t=l), 0), 0), j=1..nops(l))))
        end:
    g:= (n, i, l)-> `if`(n=0 or i=1, b([1$n, l[]], nops(l)+n),
                     add(g(n-i*j, i-1, [i$j, l[]]), j=0..n/i)):
    T:= n-> (p-> seq(coeff(p, x, i), i=0..degree(p)))(g(n$2, [])):
    seq(T(n), n=0..10);
    # second Maple program (counting ballot sequences):
    b:= proc(n, v, l) option remember; local w; w:=add(t, t=l);
          `if`(n<1, 1, expand(add(`if`(i=1 or l[i-1]>l[i],
          `if`(v(p-> seq(coeff(p, x, i), i=0..degree(p)))(b(n-1, 1, [1])):
    seq(T(n), n=0..10);
  • Mathematica
    b[l_List, i_] := b[l, i] = If[l == {}, 1, Expand[Sum[ If[l[[j]] > If[j == 1, 0, l[[j-1]]], If[j == 1 && l[[j]] == 1, b[ReplacePart[l, 1 -> Sequence[]], j-1], b[ReplacePart[l, j -> l[[j]]-1], j]]*x^If[j>i, Total[l], 0], 0], {j, 1, Length[l]}]]] ; g[n_, i_, l_List] := g[n, i, l] = If[n == 0 || i == 1, b[Join[Array[1&, n], l], Length[l]+n], Sum[g[n-i*j, i-1, Join[Array[i&, j], l]], {j, 0, n/i}]]; T[n_] := Function[{p}, Table[Coefficient[p, x, i], {i, 0, Exponent[p, x]}]][g[n, n, {}]]; Table[T[n], {n, 0, 10}] // Flatten (* Jean-François Alcover, Jan 14 2015, translated from Maple *)

A275416 Triangle read by rows: T(n,k) is the number of multisets of k odd numbers with a cap of the total sum set to n.

Original entry on oeis.org

1, 1, 1, 2, 1, 1, 2, 3, 1, 1, 3, 4, 3, 1, 1, 3, 8, 5, 3, 1, 1, 4, 10, 10, 5, 3, 1, 1, 4, 16, 15, 11, 5, 3, 1, 1, 5, 20, 27, 17, 11, 5, 3, 1, 1, 5, 29, 38, 32, 18, 11, 5, 3, 1, 1, 6, 35, 60, 49, 34, 18, 11, 5, 3, 1, 1, 6, 47, 84, 83, 54, 35, 18, 11, 5, 3, 1, 1, 7, 56, 122, 123
Offset: 1

Views

Author

R. J. Mathar, Jul 27 2016

Keywords

Comments

By considering the partitions of n into k parts we set a cap on the odd numbers of each part and count the multisets (ordered k-tuples) of odd numbers where each number is not larger than the cap of its part.
Multiset transformation of A110654 or A065033.

Examples

			T(6,2) = 3+2+3 = 8 counts {1,1} {1,3}, and {3,3} from taking two odd numbers <= 3; it counts {1,1} and {1,3} from taking an odd number <= 2 and an odd number <= 4; and it counts {1,1}, {1,3} and {1,5} from taking an odd number <= 1 and an odd number <= 5.
T(6,3) = 1+2+2 = 5 counts {1,1,1} from taking three odd numbers <= 2; it counts {1,1,1} and {1,1,3} from taking an odd number <= 1 and an odd number <= 2 and an odd number <= 3; and it counts {1,1,1} and {1,1,3} from taking two odd numbers <= 1 and an odd number <= 4.
  1
  1   1
  2   1   1
  2   3   1   1
  3   4   3   1   1
  3   8   5   3   1   1
  4  10  10   5   3   1   1
  4  16  15  11   5   3   1   1
  5  20  27  17  11   5   3   1   1
  5  29  38  32  18  11   5   3   1   1
  6  35  60  49  34  18  11   5   3   1   1
  6  47  84  83  54  35  18  11   5   3   1   1
  7  56 122 123  94  56  35  18  11   5   3   1   1
  7  72 164 192 146  99  57  35  18  11   5   3   1   1
		

Crossrefs

Cf. A110654 (column 1), A003293 (row sums?), A089353 (equivalent Multiset transformation of A000027), A005232 (2nd column?), A097513 (3rd column?).
T(2n,n) gives A269628.

Programs

  • Maple
    b:= proc(n, i, p) option remember; `if`(p>n, 0, `if`(n=0, 1,
          `if`(min(i, p)<1, 0, add(b(n-i*j, i-1, p-j)*
           binomial(ceil(i/2)+j-1, j), j=0..min(n/i, p)))))
        end:
    T:= (n, k)-> b(n$2, k):
    seq(seq(T(n, k), k=1..n), n=1..16);  # Alois P. Heinz, Apr 13 2017
  • Mathematica
    b[n_, i_, p_] := b[n, i, p] = If[p > n, 0, If[n == 0, 1, If[Min[i, p] < 1, 0, Sum[b[n - i*j, i - 1, p - j]*Binomial[Ceiling[i/2] + j - 1, j], {j, 0, Min[n/i, p]}]]]];
    T[n_, k_] := b[n, n, k];
    Table[T[n, k], {n, 1, 16}, {k, 1, n}] // Flatten (* Jean-François Alcover, May 19 2018, after Alois P. Heinz *)

Formula

T(n,1) = A110654(n).
T(n,k) = Sum_{c_i*N_i=n,i=1..k} binomial(T(N_i,1)+c_i-1,c_i) for 1 < k <= n.
G.f.: Product_{j>=1} (1-y*x^j)^(-ceiling(j/2)). - Alois P. Heinz, Apr 13 2017

A323451 Number of ways to fill a Young diagram with positive integers summing to n such that all rows and columns are strictly increasing.

Original entry on oeis.org

1, 1, 1, 3, 3, 6, 9, 12, 19, 27, 39, 54, 79, 107, 150, 209, 282, 387, 525, 707, 949, 1272, 1688, 2244, 2968, 3902, 5125, 6712, 8752, 11383, 14780, 19109, 24671, 31768, 40791, 52280, 66860, 85296, 108621, 138054, 175085, 221676, 280161, 353414, 445098, 559661
Offset: 0

Views

Author

Gus Wiseman, Jan 16 2019

Keywords

Comments

A generalized Young tableau of shape y is an array obtained by replacing the dots in the Ferrers diagram of y with positive integers.

Examples

			The a(8) = 19 generalized Young tableaux:
  8   1 7   2 6   3 5   1 2 5   1 3 4
.
  1   2   3   1 2   1 5   1 3   1 4   2 3   1 2   1 2 3
  7   6   5   5     2     4     3     3     2 3   2
.
  1   1   1 2
  2   3   2
  5   4   3
		

Crossrefs

Programs

  • Mathematica
    primeMS[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
    sqfacs[n_]:=If[n<=1,{{}},Join@@Table[Map[Prepend[#,d]&,Select[sqfacs[n/d],Min@@#>=d&]],{d,Select[Rest[Divisors[n]],SquareFreeQ]}]];
    ptnplane[n_]:=Union[Map[primeMS,Join@@Permutations/@sqfacs[n],{2}]];
    Table[Sum[Length[Select[ptnplane[Times@@Prime/@y],And@@(LessEqual@@@Transpose[PadRight[#]/.(0->Infinity)])&&And@@(UnsameQ@@@DeleteCases[Transpose[PadRight[#]],0,{2}])&]],{y,IntegerPartitions[n]}],{n,10}]

Extensions

a(21)-a(45) from Seiichi Manyama, Aug 19 2020

A323580 Number of ways to fill a Young diagram with positive integers summing to n such that the rows are weakly decreasing and the columns are weakly increasing.

Original entry on oeis.org

1, 1, 3, 6, 13, 23, 45, 76, 136, 225, 381, 611, 1001, 1570, 2489, 3842, 5948, 9022, 13714, 20501, 30649, 45262, 66721, 97393, 141888, 204993
Offset: 0

Views

Author

Gus Wiseman, Jan 18 2019

Keywords

Examples

			The a(5) = 23 tableaux:
  5   41   32   311   221   2111   11111
.
  1   2   11   21   11   111   111   1111
  4   3   3    2    21   2     11    1
.
  1   1   11   11   111
  1   2   1    11   1
  3   2   2    1    1
.
  1   11
  1   1
  1   1
  2   1
.
  1
  1
  1
  1
  1
		

Crossrefs

Programs

  • Mathematica
    primeMS[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
    facs[n_]:=If[n<=1,{{}},Join@@Table[Map[Prepend[#,d]&,Select[facs[n/d],Min@@#>=d&]],{d,Rest[Divisors[n]]}]];
    Table[Sum[Length[Select[Reverse/@Sort/@Map[primeMS,facs[y],{2}],And@@(GreaterEqual@@@Transpose[PadRight[#]])&]],{y,Times@@Prime/@#&/@IntegerPartitions[n]}],{n,10}]

A005308 Bosonic string states.

Original entry on oeis.org

1, 0, 0, 0, 1, 1, 2, 2, 4, 4, 7, 8, 14, 16, 25, 31, 47, 58, 85, 107, 153, 195, 271, 348, 480, 616, 834, 1077, 1445, 1863, 2478, 3194, 4216, 5431, 7118, 9157, 11942, 15329, 19884, 25485, 32916, 42090, 54147, 69093, 88563, 112769, 144056, 183028, 233112, 295525
Offset: 1

Views

Author

Keywords

Comments

See the reference for precise definition.

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Programs

  • Mathematica
    nmax = 50; Rest[CoefficientList[Series[x/(1-x)*Product[1/(1-x^k)^((2*k - 5 + (-1)^k)/4), {k, 1, nmax}], {x, 0, nmax}], x]] (* Vaclav Kotesovec, Aug 10 2016 *)

Formula

G.f.: Product (1 - x^k)^{-c(k)}; c(k) = 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, ....
Euler transform gives sequence with g.f. = x^3/((x+1)*(x-1)^2), Simon Plouffe, Master's Thesis, UQAM 1992.
a(n) ~ 2^(1/4) * exp(1/24 - 25*Pi^4/(3456*Zeta(3)) - 5*Pi^2 * n^(1/3) / (24*Zeta(3)^(1/3)) + 3*Zeta(3)^(1/3) * n^(2/3)/2) / (A^(1/2) * sqrt(3) * Zeta(3)^(23/72) * n^(13/72)), where A = A074962 is the Glaisher-Kinkelin constant. - Vaclav Kotesovec, Sep 26 2016

A262803 Expansion of Product_{k>=1} (1 + x^k) / (1 - x^k)^k.

Original entry on oeis.org

1, 2, 5, 12, 26, 54, 110, 214, 409, 764, 1400, 2520, 4475, 7828, 13532, 23124, 39102, 65472, 108658, 178786, 291883, 472984, 761119, 1216696, 1932898, 3052462, 4793464, 7487122, 11634771, 17991760, 27692230, 42431778, 64737414, 98360742, 148853817, 224405254
Offset: 0

Views

Author

Vaclav Kotesovec, Oct 02 2015

Keywords

Comments

Convolution of A000219 and A000009.

Examples

			G.f. = 1 + 2*x + 5*x^2 + 12*x^3 + 26*x^4 + 54*x^5 + 110*x^6 + 214*x^7 + 409*x^8 + ...
		

Crossrefs

Programs

  • Mathematica
    nmax = 40; CoefficientList[Series[Product[(1+x^k)/(1-x^k)^k, {k, 1, nmax}], {x, 0, nmax}], x]
  • PARI
    {a(n) = if( n<0, 0, polcoeff( prod(k=1, n, (1 - x^k)^-(k%2 + k), 1 + x * O(x^n)), n))}; /* Michael Somos, Oct 02 2015 */

Formula

a(n) ~ exp(1/12 - Pi^4/(1728*zeta(3)) + Pi^2 * n^(1/3)/(3*2^(7/3)*zeta(3)^(1/3)) + 3*zeta(3)^(1/3) * n^(2/3)/2^(2/3)) * zeta(3)^(7/36) / (A * sqrt(3*Pi) * 2^(29/36) * n^(25/36)), where zeta(3) = A002117 and A = A074962 is the Glaisher-Kinkelin constant.
Euler transform of [ 2, 2, 4, 4, 6, 6, ...]. - Michael Somos, Oct 02 2015
G.f.: Product_{k>0} (1 - x^k)^-(k + (k mod 2)). - Michael Somos, Oct 02 2015
Convolution square of A003293. - Michael Somos, Oct 02 2015

A002985 Number of trees in an n-node wheel.

Original entry on oeis.org

1, 1, 1, 2, 3, 6, 11, 20, 36, 64, 108, 179, 292, 464, 727, 1124, 1714, 2585, 3866, 5724, 8418, 12290, 17830, 25713, 36898, 52664, 74837, 105873, 149178, 209364, 292793, 407990, 566668, 784521, 1082848, 1490197, 2045093, 2798895, 3820629, 5202085
Offset: 1

Views

Author

Keywords

Comments

This is the number of nonequivalent spanning trees of the n-wheel graph up to isomorphism of the trees.

Examples

			All trees that span a wheel on 5 nodes are equivalent to one of the following:
      o         o         o
      |         | \     /   \
   o--o--o   o--o  o   o--o  o
      |         |           /
      o         o         o
		

References

  • F. Harary, P. E. O'Neil, R. C. Read and A. J. Schwenk, The number of trees in a wheel, in D. J. A. Welsh and D. R. Woodall, editors, Combinatorics. Institute of Mathematics and Its Applications. Southend-on-Sea, England, 1972, pp. 155-163.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Programs

  • Mathematica
    terms = 40;
    A003293[n_] := SeriesCoefficient[Product[(1-x^k)^(-Ceiling[k/2]), {k, 1, terms}], {x, 0, n}];
    A008804[n_] := SeriesCoefficient[1/((1-x)^4 (1+x)^2 (1+x^2)), {x, 0, n}];
    a[n_] := A003293[n-1] - A008804[n-3];
    Array[a, terms] (* Jean-François Alcover, Sep 02 2019 *)
  • PARI
    \\ here b(n) is A003293 and d(n) is A008804.
    b(n)={polcoeff( prod(k=1, n, (1-x^k+x*O(x^n))^-ceil(k/2)), n)}
    d(n)={(84+12*(-1)^n+6*I*((-I)^n-I^n)+(85+3*(-1)^n)*n+24*n^2+2*n^3)/96}
    a(n)=b(n-1)-d(n-3); \\ Andrew Howroyd, Oct 09 2017

Formula

a(n) = A003293(n-1) - A008804(n-3). - Andrew Howroyd, Oct 09 2017

Extensions

Terms a(32) and beyond from Andrew Howroyd, Oct 09 2017

A323581 Number of ways to fill a Young diagram with positive integers summing to n such that the rows are strictly increasing and the columns are strictly decreasing.

Original entry on oeis.org

1, 1, 1, 3, 3, 5, 8, 10, 14, 19, 28, 34, 48, 60, 80, 106, 134, 171, 222, 279, 354, 452, 562, 706, 884, 1100
Offset: 0

Views

Author

Gus Wiseman, Jan 18 2019

Keywords

Examples

			The a(8) = 14 tableaux:
  8   1 7   2 6   3 5   1 2 5   1 3 4
.
  7   6   5   2 5   3 4   2 3
  1   2   3   1     1     1 2
.
  5   4
  2   3
  1   1
		

Crossrefs

Programs

  • Mathematica
    primeMS[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
    sqfacs[n_]:=If[n<=1,{{}},Join@@Table[Map[Prepend[#,d]&,Select[sqfacs[n/d],Min@@#>=d&]],{d,Select[Rest[Divisors[n]],SquareFreeQ]}]];
    Table[Sum[Length[Select[Reverse/@Sort/@Map[primeMS,sqfacs[y],{2}],And@@Greater@@@DeleteCases[Transpose[PadRight[#]],0,{2}]&]],{y,Times@@Prime/@#&/@IntegerPartitions[n]}],{n,10}]

A319106 Expansion of Product_{k>=1} (1 + x^k)^ceiling(k/2).

Original entry on oeis.org

1, 1, 1, 3, 4, 7, 11, 17, 26, 40, 60, 88, 131, 190, 276, 398, 568, 806, 1142, 1603, 2242, 3124, 4328, 5973, 8214, 11249, 15349, 20879, 28297, 38235, 51513, 69190, 92674, 123811, 164961, 219248, 290705, 384537, 507515, 668376, 878339, 1151899, 1507679, 1969503, 2567976, 3342227
Offset: 0

Views

Author

Ilya Gutkovskiy, Sep 10 2018

Keywords

Comments

Weigh transform of 1, 1, 2, 2, 3, 3, 4, 4, ... (A110654).

Crossrefs

Programs

  • Maple
    a:=series(mul((1+x^k)^ceil(k/2),k=1..100),x=0,46): seq(coeff(a,x,n),n=0..45); # Paolo P. Lava, Apr 02 2019
  • Mathematica
    nmax = 45; CoefficientList[Series[Product[(1 + x^k)^Ceiling[k/2], {k, 1, nmax}], {x, 0, nmax}], x]
    nmax = 45; CoefficientList[Series[Product[((1 + x^(2 k - 1))(1 + x^(2 k)))^k, {k, 1, nmax}], {x, 0, nmax}], x]
    a[n_] := a[n] = If[n == 0, 1, Sum[Sum[(-1)^(k/d + 1) d Ceiling[d/2], {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[a[n], {n, 0, 45}]

Formula

G.f.: Product_{k>=1} (1 + x^k)^A110654(k).
G.f.: Product_{k>=1} ((1 + x^(2*k-1))*(1 + x^(2*k)))^k.
G.f.: exp(Sum_{k>=1} ( Sum_{d|k} (-1)^(k/d+1)*d*ceiling(d/2) ) * x^k/k).
a(n) ~ exp(3^(4/3) * Zeta(3)^(1/3) * n^(2/3) / 2^(5/3) + Pi^2 * n^(1/3) / (2^(10/3) * 3^(4/3) * Zeta(3)^(1/3)) - Pi^4 / (2^7 * 3^4 * Zeta(3))) * Zeta(3)^(1/6) / (2^(7/8) * 3^(1/3) * sqrt(Pi) * n^(2/3)). - Vaclav Kotesovec, Sep 11 2018
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