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 1-5 of 5 results.

A197126 Triangle T(n,k), n>=1, 1<=k<=n, read by rows: T(n,k) is the number of cliques of size k in all partitions of n.

Original entry on oeis.org

1, 1, 1, 3, 0, 1, 4, 2, 0, 1, 8, 2, 1, 0, 1, 11, 4, 2, 1, 0, 1, 19, 5, 3, 1, 1, 0, 1, 26, 10, 3, 3, 1, 1, 0, 1, 41, 11, 7, 3, 2, 1, 1, 0, 1, 56, 20, 8, 5, 3, 2, 1, 1, 0, 1, 83, 25, 13, 6, 5, 2, 2, 1, 1, 0, 1, 112, 38, 17, 11, 5, 5, 2, 2, 1, 1, 0, 1, 160, 49, 25, 13, 9, 5, 4, 2, 2, 1, 1, 0, 1
Offset: 1

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Author

Alois P. Heinz, Oct 10 2011

Keywords

Comments

All parts of a number partition with the same value form a clique. The size of a clique is the number of elements in the clique.

Examples

			T(4,1) = 4: [1,1,(2)], [(1),(3)], [(4)].
T(8,3) = 3: [1,1,(2,2,2)], [(1,1,1),2,3], [(1,1,1),5].
T(12,4) = 11: [(1,1,1,1),(2,2,2,2)], [1,(2,2,2,2),3], [(1,1,1,1),2,3,3], [(3,3,3,3)], [(1,1,1,1),2,2,4], [(2,2,2,2),4], [(1,1,1,1),4,4], [(1,1,1,1),3,5], [(1,1,1,1),2,6], [(1,1,1,1),8].  Here the first partition contains 2 cliques.
Triangle begins:
   1;
   1,  1;
   3,  0, 1;
   4,  2, 0, 1;
   8,  2, 1, 0, 1;
  11,  4, 2, 1, 0, 1;
  19,  5, 3, 1, 1, 0, 1;
  26, 10, 3, 3, 1, 1, 0, 1;
  ...
		

Crossrefs

Row sums give: A000070(n-1). Diagonal gives: A000012. Limit of reversed rows: T(2*n+1,n+1) = A002865(n).
Cf. A213180.

Programs

  • Maple
    b:= proc(n, p, k) option remember; `if`(n=0, [1, 0], `if`(p<1, [0, 0],
          add((l->`if`(m=k, l+[0, l[1]], l))(b(n-p*m, p-1, k)), m=0..n/p)))
        end:
    T:= (n, k)-> b(n, n, k)[2]:
    seq(seq(T(n, k), k=1..n), n=1..20);
  • Mathematica
    Table[CoefficientList[ 1/q* Tr[Flatten[q^Map[Length, Split /@ IntegerPartitions[n], {2}]]], q], {n, 24}] (* Wouter Meeussen, Apr 21 2012 *)
    b[n_, p_, k_] := b[n, p, k] = If[n == 0, {1, 0}, If[p < 1, {0, 0}, Sum[ Function[l, If[m == k, l + {0, l[[1]]}, l]][b[n - p*m, p - 1, k]], {m, 0, n/p}]]]; T[n_, k_] := b[n, n, k][[2]]; Table[Table[T[n, k], {k, 1, n}], {n, 1, 20}] // Flatten (* Jean-François Alcover, Aug 29 2016, after Alois P. Heinz *)

Formula

G.f. of column k: (x^k/(1-x^k)-x^(k+1)/(1-x^(k+1)))/Product_{j>0}(1-x^j).
Column k is asymptotic to exp(Pi*sqrt(2*n/3)) / (k*(k+1)*Pi*2^(3/2)*sqrt(n)). - Vaclav Kotesovec, May 24 2018

A116644 Triangle read by rows: T(n,k) is the number of partitions of n having exactly k doubletons (n>=0, k>=0). By a doubleton in a partition we mean an occurrence of a part exactly twice (the partition [4,(3,3),2,2,2,(1,1)] has two doubletons, shown between parentheses).

Original entry on oeis.org

1, 1, 1, 1, 3, 3, 2, 5, 2, 8, 2, 1, 10, 5, 13, 8, 1, 20, 9, 1, 26, 12, 4, 33, 21, 2, 46, 25, 5, 1, 58, 37, 6, 75, 48, 11, 1, 101, 59, 16, 125, 84, 19, 3, 157, 115, 23, 2, 206, 135, 39, 5, 253, 187, 46, 4, 317, 238, 63, 8, 1, 403, 292, 90, 7, 494, 382, 108, 17, 1, 608, 490, 139, 18
Offset: 0

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Author

Emeric Deutsch, Feb 20 2006

Keywords

Comments

Apparently, rows n with p(p+1)<=n<(p+1)(p+2) have at most p+1 terms. Row sums are the partition numbers (A000041). T(n,0)=A116645(n). Sum(k*T(n,k),k>=0)=A116646(n).

Examples

			T(6,2) = 1 because [2,2,1,1] is the only partition of 6 with 2 doubletons.
Triangle starts:
1;
1;
1,  1;
3;
3,  2;
5,  2;
8,  2, 1;
10, 5;
13, 8, 1;
		

Crossrefs

Programs

  • Maple
    g:=product(1+x^j+t*x^(2*j)+x^(3*j)/(1-x^j),j=1..35): gser:=simplify(series(g,x=0,35)): P[0]:=1: for n from 1 to 24 do P[n]:=coeff(gser,x^n) od: for n from 0 to 24 do seq(coeff(P[n],t,j),j=0..degree(P[n])) od; # sequence given in triangular form

Formula

G.f.: G(t,x) = product(1+x^j+tx^(2j)+x^(3j)/(1-x^j), j=1..infinity).

A117524 Total number of parts of multiplicity 3 in all partitions of n.

Original entry on oeis.org

0, 0, 1, 0, 1, 2, 3, 3, 7, 8, 13, 17, 25, 32, 48, 59, 83, 108, 145, 183, 247, 310, 406, 512, 659, 824, 1055, 1307, 1651, 2047, 2558, 3146, 3913, 4788, 5904, 7202, 8821, 10707, 13054, 15770, 19118, 23027, 27775, 33312, 40029, 47835, 57231, 68182, 81261
Offset: 1

Views

Author

Vladeta Jovovic, Apr 26 2006

Keywords

Examples

			a(9) = 7 because among the 30 (=A000041(9)) partitions of 9 only [6,(1,1,1)],[4,2,(1,1,1)],[(3,3,3)],[3,3,(1,1,1)],[3,(2,2,2)],[(2,2,2),(1,1,1)] contain parts of multiplicity 3 and their total number is 7 (shown between parentheses)
		

Crossrefs

Cf. A024786, A116646. Column k=3 of A197126.

Programs

  • Maple
    g:=(x^3/(1-x^3)-x^4/(1-x^4))/product(1-x^i,i=1..65): gser:=series(g,x=0,62): seq(coeff(gser,x,n),n=1..58); # Emeric Deutsch, Apr 29 2006

Formula

G.f. for total number of parts of multiplicity m in all partitions of n is (x^m/(1-x^m)-x^(m+1)/(1-x^(m+1)))/Product(1-x^i,i=1..infinity).
a(n) = Sum(k*A118806(n,k), k>=0). - Emeric Deutsch, Apr 29 2006
a(n) ~ exp(Pi*sqrt(2*n/3)) / (24*Pi*sqrt(2*n)). - Vaclav Kotesovec, May 24 2018

A213180 Sum over all partitions lambda of n of Sum_{p:lambda} p^m(p,lambda), where m(p,lambda) is the multiplicity of part p in lambda.

Original entry on oeis.org

0, 1, 3, 7, 16, 28, 59, 91, 170, 269, 450, 655, 1162, 1602, 2527, 3793, 5805, 8034, 12660, 17131, 26484, 37384, 53738, 73504, 114683, 153613, 221225, 313339, 453769, 609179, 927968, 1223909, 1804710, 2522264, 3539835, 4855420, 7439870, 9765555, 14009545
Offset: 0

Views

Author

Alois P. Heinz, Feb 27 2013

Keywords

Examples

			a(6) = 59: (1^6) + (2+1^4) + (2^2+1^2) + (2^3) + (3+1^3) + (3+2+1) + (3^2) + (4+1^2) + (4+2) + (5+1) + (6) = 1+3+5+8+4+6+9+5+6+6+6 = 59.
		

Crossrefs

Cf. A000070 (Sum 1), A006128 (Sum m), A014153 (Sum p), A024786 (Sum floor(1/m)), A066183 (Sum p^2*m), A066186 (Sum p*m), A073336 (Sum floor(m/p)), A116646 (Sum delta(m,2)), A117524 (Sum delta(m,3)), A103628 (Sum delta(m,1)*p), A117525 (Sum delta(m,2)*p), A197126, A213191.

Programs

  • Maple
    b:= proc(n, p) option remember; `if`(n=0, [1, 0], `if`(p<1, [0, 0],
          add((l->`if`(m=0, l, l+[0, l[1]*p^m]))(b(n-p*m, p-1)), m=0..n/p)))
        end:
    a:= n-> b(n, n)[2]:
    seq(a(n), n=0..40);
  • Mathematica
    b[n_, p_] := b[n, p] = If[n==0, {1, 0}, If[p<1, {0, 0}, Sum[Function[l, If[m==0, l, l+{0, l[[1]]*p^m}]][b[n-p*m, p-1]], {m, 0, n/p}]]]; a[n_] := b[n, n][[2]]; Table[a[n], {n, 0, 40}] (* Jean-François Alcover, Feb 15 2017, translated from Maple *)

Formula

From Vaclav Kotesovec, May 24 2018: (Start)
a(n) ~ c * 3^(n/3), where
c = 5.0144820680945600131204662934686439430547... if mod(n,3)=0
c = 4.6144523178014379613985400559486878971522... if mod(n,3)=1
c = 4.5237761454818383598444208605033385016299... if mod(n,3)=2
(End)

A316861 a(n) = Sum_{p in P} y(1)*y(2), where P is the set of partitions of n, and y(k) is the number of parts with multiplicity at least k in p.

Original entry on oeis.org

0, 0, 1, 1, 4, 7, 13, 22, 38, 58, 93, 139, 208, 302, 438, 616, 869, 1200, 1650, 2239, 3026, 4038, 5374, 7081, 9292, 12103, 15704, 20236, 25992, 33191, 42237, 53490, 67524, 84860, 106341, 132736, 165212, 204928, 253518, 312629, 384585, 471734, 577276, 704584, 858078
Offset: 0

Views

Author

Emily Anible, Jul 15 2018

Keywords

Comments

Also (1/2)*Sum_{p in P} H(1)*H(2), where P is the set of partitions of n, and H(k) is the number of k-hooks in p.

Examples

			For n=6, we sum over the partitions of 6. For each partition, we count the parts with multiplicity at least one, and those of at least two.
6............y(1)*y(2) = 1*0 = 0
5,1..........y(1)*y(2) = 2*0 = 0
4,2..........y(1)*y(2) = 2*0 = 0
4,1,1........y(1)*y(2) = 2*1 = 2
3,3..........y(1)*y(2) = 1*1 = 1
3,2,1........y(1)*y(2) = 3*0 = 0
3,1,1,1......y(1)*y(2) = 2*1 = 2
2,2,2........y(1)*y(2) = 1*1 = 1
2,2,1,1......y(1)*y(2) = 2*2 = 4
2,1,1,1,1....y(1)*y(2) = 2*1 = 2
1,1,1,1,1,1..y(1)*y(2) = 1*1 = 1
--------------------------------
Total.........................13
		

Crossrefs

Programs

  • Maple
    b:= proc(n, i, x, y) option remember;
         `if`(n=0, x*y, `if`(i<1, 0, add(b(n-i*j, i-1,
         `if`(j>0, 1, 0)+x, `if`(j>1, 1, 0)+y), j=0..n/i)))
        end:
    a:= n-> b(n$2, 0$2):
    seq(a(n), n=0..55);  # Alois P. Heinz, Jul 30 2018
  • Mathematica
    Array[Total[
       Count[Split@#, (_?(Length@# >= 1 &))] Count[
           Split@#, (_?(Length@# >= 2 &))] & /@
        IntegerPartitions[#]] &, 50]
    (* Second program: *)
    b[n_, i_, x_, y_] := b[n, i, x, y] = If[n == 0, x*y, If[i < 1, 0, Sum[b[n - i*j, i - 1, If[j > 0, 1, 0] + x, If[j > 1, 1, 0] + y], {j, 0, n/i}]]];
    a[n_] := b[n, n, 0, 0];
    a /@ Range[0, 55] (* Jean-François Alcover, Sep 16 2019, after Alois P. Heinz *)
  • PARI
    seq(n)={Vec(x*(1 + x^2 + x^3)/((1 - x)^2*(1 + x)*(1 + x + x^2)*prod(i=1, n-1, 1 - x^i + O(x^n))) + O(x^n), -n)} \\ Andrew Howroyd, Jul 15 2018

Formula

G.f.: (q^3/((1-q)(1-q^2)) + q^2/(1-q^2) - q^3/(1-q^3))*Product_{j>=1} 1/(1-q^j).
a(n) = A000097(n+3) + A116646(n).
In general, Sum_{n>=0} q^n Sum_{p in P} y(s)*y(t) for s < t is given by (q^(s+t)/((1-q^s)(1-q^t)) + q^t/(1-q^t) - q^(s+t)/(1-q^(s+t))) * Product_{j>=1} 1/(1-q^j).
Showing 1-5 of 5 results.