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 1-4 of 4 results.

A091298 Triangle read by rows: T(n,k) is the number of plane partitions of n containing exactly k parts.

Original entry on oeis.org

1, 1, 2, 1, 2, 3, 1, 4, 3, 5, 1, 4, 7, 5, 7, 1, 6, 10, 13, 7, 11, 1, 6, 14, 20, 19, 11, 15, 1, 8, 18, 33, 32, 31, 15, 22, 1, 8, 25, 43, 56, 54, 43, 22, 30, 1, 10, 29, 66, 81, 99, 78, 64, 30, 42, 1, 10, 37, 83, 126, 150, 148, 118, 88, 42, 56, 1, 12, 44, 114, 174, 246, 235, 230, 166, 124, 56, 77
Offset: 1

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Author

Wouter Meeussen, Feb 24 2004

Keywords

Comments

First column is 1, representing the single-part {{n}}, last column is P(n), since the all-ones plane partitions form the Ferrers-Young plots of the (linear) partitions of n.
A plane partition of n is a two-dimensional table (or matrix) with nonnegative elements summing up to n, and nonincreasing rows and columns. (Zero rows and columns are ignored.) - M. F. Hasler, Sep 22 2018

Examples

			This plane partition of n=7: {{3,1,1},{2}} contains 4 parts: 3,1,1,2.
Triangle T(n,k) begins:
  1;
  1,  2;
  1,  2,  3;
  1,  4,  3,  5;
  1,  4,  7,  5,  7;
  1,  6, 10, 13,  7, 11;
  1,  6, 14, 20, 19, 11, 15;
  1,  8, 18, 33, 32, 31, 15, 22;
  1,  8, 25, 43, 56, 54, 43, 22, 30;
  1, 10, 29, 66, 81, 99, 78, 64, 30, 42;
  ...
		

Crossrefs

Row sums give A000219.
Column 1 is A000012. Column 2 is A052928. Diagonal and subdiagonal are A000041.

Programs

  • Mathematica
    (* see A089924 for "planepartition" *) Table[Length /@ Split[Sort[Length /@ Flatten /@ planepartitions[n]]], {n, 16}]
  • PARI
    A091298(n,k)=sum(i=1,#n=PlanePartitions(n),sum(j=1,#n[i],#n[i][j])==k)
    PlanePartitions(n,L=0,PP=List())={ n<2&&return([if(n,[[1]],[])]); for(N=1,n, my(P=apply(Vecrev, if(L, select(p->vecmin(L-Vecrev(p,#L))>=0, partitions(N,L[1],#L)), partitions(N)))); if(NM. F. Hasler, Sep 24 2018

A081105 5th binomial transform of (1,1,0,0,0,0,.....).

Original entry on oeis.org

1, 6, 35, 200, 1125, 6250, 34375, 187500, 1015625, 5468750, 29296875, 156250000, 830078125, 4394531250, 23193359375, 122070312500, 640869140625, 3356933593750, 17547607421875, 91552734375000, 476837158203125
Offset: 0

Views

Author

Paul Barry, Mar 07 2003

Keywords

Comments

Main diagonal of array defined by m(1,j)=j; m(i,1)=i and m(i,j)=m(i-1,j)+4*m(i-1,j-1) - Benoit Cloitre, Jun 13 2003

Crossrefs

Programs

Formula

a(n) = 10*a(n-1)-25*a(n-2), a(0)=1, a(1)=6.
a(n) = (n+5)*5^(n-1).
G.f.: (1-4x)/(1-5x)^2.
a(n) = A079027(n), n>0. - R. J. Mathar, Sep 18 2008
From Amiram Eldar, Jan 19 2021: (Start)
Sum_{n>=0} 1/a(n) = 15625*log(5/4) - 41825/12.
Sum_{n>=0} (-1)^n/a(n) = 15625*log(6/5) - 34175/12. (End)

A090539 Total number of parts equal to 1 in all plane partitions of n.

Original entry on oeis.org

0, 1, 4, 11, 28, 62, 137, 278, 561, 1080, 2051, 3778, 6885, 12255, 21589, 37409, 64160, 108612, 182234, 302461, 497997, 812579, 1316225, 2115608, 3378239, 5357855, 8447086, 13237631, 20632630, 31985504, 49339795, 75738099, 115731636, 176055280, 266697522
Offset: 0

Views

Author

Wouter Meeussen, Feb 01 2004

Keywords

Crossrefs

Column k=1 of A092288.

Programs

Extensions

a(18)-a(27) from Vaclav Kotesovec, May 05 2018
a(28)-a(34) from Alois P. Heinz, Sep 24 2018

A319648 Total number of parts in all plane partitions of n.

Original entry on oeis.org

0, 1, 5, 14, 38, 85, 196, 401, 830, 1615, 3119, 5802, 10718, 19246, 34276, 59889, 103656, 176801, 299025, 499732, 828638, 1360696, 2218128, 3586194, 5759839, 9184715, 14557974, 22929745, 35916469, 55942850, 86695329, 133671740, 205144324, 313380895, 476667370
Offset: 0

Views

Author

Alois P. Heinz, Sep 25 2018

Keywords

Examples

			The plane partitions of 2 are [2], [1 1] and [1; 1]. There is a total of a(2) = 5 parts. - _M. F. Hasler_, Sep 27 2018
		

Crossrefs

Row sums of A092288.
Cf. A000219.

Programs

  • PARI
    A319648(n)={vecsum(apply(pp->vecsum(apply(p->#p,pp)),PlanePartitions(n)))} \\ See A091298 for PlanePartitions(). For illustration mainly, becomes slow for n > 15. - M. F. Hasler, Sep 27 2018
    
  • PARI
    M319648=[]; A319648(n,L=0,s)={if(L, n>1||return([1,1]); #L>2||(s=setsearch(M319648,[[n,L],[]],1))>#M319648|| M319648[s][1]!=[n,L]|| return(M319648[s][2]); my(S=[1,n]); for(m=2,n, forpart(P=m, vecmin(L-Vecrev(P,#L))<0&&next; S+=if(mA319648(n-m,Vecrev(P))*[1,#P;0,1],[1,#P]),L[1],#L)); #L>2|| M319648=setunion(M319648,[[[n,L],S]]); S, my(S=n); n>1&& forpart(P=n,S+=#P); for(m=2,n-1,forpart(P=m,S+=A319648(n-m,Vecrev(P))*[#P,1]~));S)} \\ M. F. Hasler, Sep 30 2018

Formula

a(n) = Sum_{k=1..n} k*A091298(n,k). - M. F. Hasler, Sep 27 2018
Showing 1-4 of 4 results.