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.

A219727 Number A(n,k) of k-partite partitions of {n}^k into k-tuples; square array A(n,k), n>=0, k>=0, read by antidiagonals.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 5, 9, 3, 1, 1, 15, 66, 31, 5, 1, 1, 52, 712, 686, 109, 7, 1, 1, 203, 10457, 27036, 6721, 339, 11, 1, 1, 877, 198091, 1688360, 911838, 58616, 1043, 15, 1, 1, 4140, 4659138, 154703688, 231575143, 26908756, 476781, 2998, 22, 1
Offset: 0

Views

Author

Alois P. Heinz, Nov 26 2012

Keywords

Comments

A(n,k) is the number of factorizations of m^n where m is a product of k distinct primes. A(2,2) = 9: (2*3)^2 = 36 has 9 factorizations: 36, 3*12, 4*9, 3*3*4, 2*18, 6*6, 2*3*6, 2*2*9, 2*2*3*3.
A(n,k) is the number of (n*k) X k matrices with nonnegative integer entries and column sums n up to permutation of rows. - Andrew Howroyd, Dec 10 2018

Examples

			A(1,3) = 5: [(1,1,1)], [(1,1,0),(0,0,1)], [(1,0,1),(0,1,0)], [(1,0,0),(0,1,0),(0,0,1)], [(0,1,1),(1,0,0)].
A(2,2) = 9: [(2,2)], [(2,1),(0,1)], [(2,0),(0,2)], [(2,0),(0,1),(0,1)], [(1,2),(1,0)], [(1,1),(1,1)], [(1,1),(1,0),(0,1)], [(1,0),(1,0),(0,2)], [(1,0),(1,0),(0,1),(0,1)].
Square array A(n,k) begins:
  1,   1,    1,      1,        1,         1,         1,       1, ...
  1,   1,    2,      5,       15,        52,       203,     877, ...
  1,   2,    9,     66,      712,     10457,    198091, 4659138, ...
  1,   3,   31,    686,    27036,   1688360, 154703688, ...
  1,   5,  109,   6721,   911838, 231575143, ...
  1,   7,  339,  58616, 26908756, ...
  1,  11, 1043, 476781, ...
  1,  15, 2998, ...
		

Crossrefs

Columns k=0..3 give: A000012, A000041, A002774, A219678.
Rows n=0..4 give: A000012, A000110, A020555, A322487, A358781.
Main diagonal gives A322488.
Cf. A188392, A219585 (partitions of {n}^k into distinct k-tuples), A256384, A318284, A318951.

Programs

  • PARI
    EulerT(v)={Vec(exp(x*Ser(dirmul(v,vector(#v,n,1/n))))-1, -#v)}
    D(p, n, k)={my(v=vector(n)); for(i=1, #p, v[p[i]]++); EulerT(v)[n]^k/prod(i=1, #v, i^v[i]*v[i]!)}
    T(n, k)={my(m=n*k, q=Vec(exp(O(x*x^m) + intformal((x^n-1)/(1-x)))/(1-x))); if(n==0, 1, sum(j=0, m, my(s=0); forpart(p=j, s+=D(p,n,k), [1,n]); s*q[#q-j]))} \\ Andrew Howroyd, Dec 11 2018

A358721 Triangle read by rows. Number T(n, k) of partitions of the multiset [1, 1, 1, 2, 2, 2, ..., n, n, n] into k nonempty submultisets, for 1 <= k <= 3n.

Original entry on oeis.org

1, 1, 1, 1, 1, 7, 11, 8, 3, 1, 1, 31, 139, 219, 175, 86, 28, 6, 1, 1, 127, 1547, 5321, 8004, 6687, 3579, 1329, 359, 71, 10, 1, 1, 511, 16171, 118605, 333887, 472784, 398771, 223700, 89640, 26853, 6171, 1100, 150, 15, 1, 1, 2047, 164651, 2511653, 13045458, 31207637, 41429946, 34621129, 19882236, 8342411, 2668319, 669446, 134075, 21591, 2785, 281, 21, 1
Offset: 0

Views

Author

Marko Riedel, Nov 28 2022

Keywords

Comments

A generalization of ordinary Stirling set numbers to multisets that contain some m instances each of n elements, here we have m=3.

Examples

			The triangular array starts:
[0]: 1,
[1]: 1,   1,    1;
[2]: 1,   7,   11,    8,    3,    1;
[3]: 1,  31,  139,  219,  175,   86,   28,    6,   1;
[4]: 1, 127, 1547, 5321, 8004, 6687, 3579, 1329, 359, 71, 10, 1;
		

References

  • F. Harary and E. Palmer, Graphical Enumeration, Academic Press, 1973.

Crossrefs

Cf. A008277, A358710, A358722, A322487 (row sums).

A331196 Number of nonnegative integer matrices with n distinct columns and any number of nonzero rows with each column sum being 3 and rows in nonincreasing lexicographic order.

Original entry on oeis.org

1, 3, 28, 599, 23243, 1440532, 131530132, 16720208200, 2837752812927, 622570020892599, 172077041175850521, 58679982298020226625, 24262822372018694983540, 11986886218243164848742812, 6987708088810202717378639087, 4754544525981425409034078100189
Offset: 0

Views

Author

Andrew Howroyd, Jan 11 2020

Keywords

Comments

The condition that the rows be in nonincreasing order is equivalent to considering nonequivalent matrices up to permutation of rows.

Examples

			The a(2) = 28 matrices include 6 with 2 rows, 10 with 3 rows, 8 with 4 rows, 3 with 5 rows and 1 with 6 rows. The 16 with 2 or 3 rows are:
   [3 2]  [3 1]  [3 0]  [2 3]  [2 1]  [2 0]  [3 1]  [3 0]
   [0 1]  [0 2]  [0 3]  [1 0]  [1 2]  [1 3]  [0 1]  [0 2]
                                             [0 1]  [0 1]
.
   [2 2]  [2 1]  [2 1]  [2 0]  [2 0]  [2 0]  [1 3]  [1 2]
   [1 0]  [1 1]  [1 0]  [1 2]  [1 1]  [1 0]  [1 0]  [1 1]
   [0 1]  [0 1]  [0 2]  [0 1]  [0 2]  [0 3]  [1 0]  [1 0]
		

Crossrefs

Row n=3 of A331161.
Cf. A322487.

Formula

a(n) = Sum_{k=0..n} Stirling1(n,k)*A322487(k).

A319591 Number of nonnegative integer matrices with n columns and any number of nonzero distinct rows with every column summing to 3 up to permutation of rows.

Original entry on oeis.org

1, 2, 17, 364, 14595, 937776, 88507276, 11584785137, 2017129470049, 452573312572094, 127585778625167901, 44275881599081757633, 18594652294164085489646, 9315786786179883210141889, 5499383628157822564248546214, 3784760890972848935690646794792
Offset: 0

Views

Author

Andrew Howroyd, Dec 16 2018

Keywords

Comments

Also, the number of factorizations of m^3 into distinct factors where m is a product of n distinct primes.

Crossrefs

Row n=3 of A219585.
Cf. A322487.

A358781 Number of multiset partitions of [1,1,1,1,2,2,2,2,...,n,n,n,n] into nonempty multisets.

Original entry on oeis.org

1, 5, 109, 6721, 911838, 231575143, 99003074679, 66106443797808, 65197274052335504, 90954424202936106523, 173398227073956386079670, 439196881673194611574668282, 1443741072199958276777413001395
Offset: 0

Views

Author

Marko Riedel, Nov 29 2022

Keywords

Comments

Generalization of Bell numbers to multiset partitions with m instances each of n different elements, here m=4.

References

  • F. Harary and E. Palmer, Graphical Enumeration, Academic Press, 1973.

Crossrefs

Row n=4 of A219727.
Showing 1-5 of 5 results.