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 1-8 of 8 results.

A188392 T(n,k) = number of (n*k) X k binary arrays with rows in nonincreasing order and n ones in every column.

Original entry on oeis.org

1, 2, 1, 5, 3, 1, 15, 16, 4, 1, 52, 139, 39, 5, 1, 203, 1750, 862, 81, 6, 1, 877, 29388, 35775, 4079, 150, 7, 1, 4140, 624889, 2406208, 507549, 15791, 256, 8, 1, 21147, 16255738, 238773109, 127126912, 5442547, 52450, 410, 9, 1, 115975, 504717929, 32867762616
Offset: 1

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Author

R. H. Hardin, Mar 30 2011

Keywords

Examples

			Array begins:
========================================================================
n\k| 1  2   3      4         5            6            7               8
---+--------------------------------------------------------------------
1  | 1  2   5     15        52          203           877           4140
2  | 1  3  16    139      1750        29388        624889       16255738
3  | 1  4  39    862     35775      2406208     238773109    32867762616
4  | 1  5  81   4079    507549    127126912   55643064708 38715666455777
5  | 1  6 150  15791   5442547   4762077620 8738543204786
6  | 1  7 256  52450  46757209 135029200594
7  | 1  8 410 154279 335279744
8  | 1  9 625 411180
9  | 1 10 915
     ...
All solutions for 6 X 2
..1..1....1..1....1..0....1..1
..1..1....1..1....1..0....1..0
..1..0....1..1....1..0....1..0
..0..1....0..0....0..1....0..1
..0..0....0..0....0..1....0..1
..0..0....0..0....0..1....0..0
		

Crossrefs

Columns 3..7 are A011863(n+1), A175707, A188389, A188390, A188391.
Main diagonal gives A188388.

Programs

  • PARI
    WeighT(v)={Vec(exp(x*Ser(dirmul(v, vector(#v,n,(-1)^(n-1)/n))))-1,-#v)}
    D(p, n, k)={my(v=vector(n)); for(i=1, #p, v[p[i]]++); WeighT(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 12 2018

A322487 Number of (3*n) X n matrices with nonnegative integer entries and each column sum being 3 up to permutation of rows.

Original entry on oeis.org

1, 3, 31, 686, 27036, 1688360, 154703688, 19692332568, 3342458334775, 732812082630803, 202322386045180686, 68898094282978653925, 28443422251718020038049, 14029033632468285836567998, 8164217197799501761637725983, 5545466507405459243366712102466
Offset: 0

Views

Author

Andrew Howroyd, Dec 11 2018

Keywords

Comments

Also number of multiset partitions of [1,1,1,2,2,2,...,n,n,n] into nonempty multisets. - Marko Riedel, Nov 29 2022

Examples

			a(1) = 3 because up to permutations of rows there are 3 column vectors with sum 3: [1, 1, 1], [2, 1, 0] and [3, 0, 0].
		

Crossrefs

Row n=3 of A219727.

A360037 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 subsets, for 3 <= k <= 3n.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 4, 10, 13, 7, 3, 1, 1, 14, 92, 221, 249, 172, 81, 25, 6, 1, 1, 50, 872, 4277, 8806, 9840, 6945, 3377, 1206, 325, 65, 10, 1, 1, 186, 8496, 85941, 320320, 585960, 627838, 442321, 221475, 82985, 24038, 5496, 995, 140, 15, 1
Offset: 1

Views

Author

Marko Riedel, Jan 22 2023

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:
[1]: 1;
[2]: 1,  1,  1,   1;
[3]: 1,  4, 10,  13,   7,   3,  1;
[4]: 1, 14, 92, 221, 249, 172, 81, 25, 6, 1;
		

References

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

Crossrefs

Row sums are A165434.

Programs

  • Maple
    read "a360037maple":  # see link
    A360037Row := n -> seq(T2(n, k, 3), k = 3..n*3): seq(A360037Row(n), n = 1..6);

A165435 Number of quad-coverings of a set.

Original entry on oeis.org

1, 1, 5, 81, 4079, 507549, 127126912, 55643064708, 38715666455777, 40095856807088486, 58901884724160709571, 118283825763578012358080, 315297447553856723754810322, 1089117884184737631305395668913, 4778248300569771278502378511288513
Offset: 0

Views

Author

Doron Zeilberger, Sep 18 2009

Keywords

Comments

Analogous to A165434. See comments and references there.

Crossrefs

Row 4 of A188392.
Cf. A165434.

A165436 Number of penta-coverings of a set.

Original entry on oeis.org

1, 1, 6, 150, 15791, 5442547, 4762077620, 8738543204786, 29476338150380267, 166824392081434701613, 1483193888081012069795493, 19709785177023094680286421698, 376477754511485610186131980496220, 10014420201202866850432679446597128835
Offset: 0

Views

Author

Doron Zeilberger, Sep 18 2009

Keywords

Comments

Analogous to A165434. See references and comments there.

Crossrefs

Row 5 of A188392.
Cf. A165434.

A175707 Number of ways to put n copies of 1,2,3,4 into sets.

Original entry on oeis.org

1, 15, 139, 862, 4079, 15791, 52450, 154279, 411180, 1009741, 2314278, 5000125, 10264997, 20152950, 38037517, 69323949, 122448455, 210271756, 351989816, 575711716, 921889652, 1447822620, 2233501928, 3389114724, 5064582169, 7461570579, 10848490675, 15579077786, 22115241763, 31054971635, 43166197978, 59427633555, 81077755892, 109673237289, 147158299390, 195946638641
Offset: 0

Views

Author

Keywords

Comments

Related to generalized Bell Numbers.
The n copies of each digit must be in different sets, and the sets must be nonempty.
Other definition: Number of ways to distribute n copies of 1,2,3,4 into an arbitrary number of (nonempty) sets. Due to the nature of sets, the same digit may not be several times in the same set.

Examples

			For n=1, the solution is the fourth term of Bell numbers A000110.
For n=2, one way to partition 2 copies of 1, 2 copies of 2, 2 copies of 3 and 2 copies of 4 is {1}{2}{34}{12}{34}. On the other hand {112}{34}{23}{4} is not allowed since the same numbers are in the same set {112}.
		

Crossrefs

Programs

  • Maple
    a:= n-> (5382*n^11 +236808*n^10 +4643760*n^9 +53507520*n^8 +402098796*n^7 +2067612624*n^6 +7421736960*n^5 +18616942080*n^4 +32101468047*n^3 +36555545268*n^2 +25131098880*n +8024016000 +7016625*(-1)^n*n^3 +84199500*(-1)^n*n^2 +359251200*(-1)^n*n +538876800*(-1)^n) /(2^11*3^7*5^2*7*11) +5/3^6*(-1)^n * (sin(n*Pi/3)/sqrt(3)+ cos(n*Pi/3));
    seq(a(n), n=0..40);
    seq(SeqBrnDJ(n,4)[5], n=1..6); # using the Maple package BABUSHKAS (see links)
  • Mathematica
    LinearRecurrence[{7, -17, 8, 36, -60, 4, 56, -22, -22, -22, 56, 4, -60, 36, 8, -17, 7, -1}, {1, 15, 139, 862, 4079, 15791, 52450, 154279, 411180, 1009741, 2314278, 5000125, 10264997, 20152950, 38037517, 69323949, 122448455, 210271756}, 36] (* Jean-François Alcover, Nov 13 2018 *)

Formula

a(n) = (5382*n^11 +236808*n^10 +4643760*n^9 +53507520*n^8 +402098796*n^7 +2067612624*n^6 +7421736960*n^5 +18616942080*n^4 +32101468047*n^3 +36555545268*n^2 +25131098880*n +8024016000 +7016625*(-1)^n*n^3 +84199500*(-1)^n*n^2 +359251200*(-1)^n*n +538876800*(-1)^n) / (2^11*3^7*5^2*7*11) +5/3^6*(-1)^n * (sin(n*Pi/3)/sqrt(3) +cos(n*Pi/3)).
Recurrence: a(n) -7*a(n-1) +17*a(n-2) -8*a(n-3) -36*a(n-4) +60*a(n-5) -4*a(n-6) -56*a(n-7) +22*a(n-8) +22*a(n-9) +22*a(n-10) -56*a(n-11) -4*a(n-12) +60*a(n-13) -36*a(n-14) -8*a(n-15) +17*a(n-16) -7*a(n-17) +a(n-18) = 0.
G.f.: (x^10 +8*x^9 +51*x^8 +136*x^7 +252*x^6 +300*x^5 +252*x^4 +136*x^3 +51*x^2 +8*x+1) / ((x^2+x+1)*(x+1)^4*(x-1)^12).

A331389 Number of binary matrices with n distinct columns and any number of nonzero rows with 3 ones in every column and rows in nonincreasing lexicographic order.

Original entry on oeis.org

1, 1, 3, 29, 666, 28344, 1935054, 193926796, 26892165502, 4946464286746, 1168900475263013, 346080409272270888, 125798338606148948325, 55204084562033205121607, 28834556615453989801860765, 17710828268156331289770544579, 12658784968736373972502731143309
Offset: 0

Views

Author

Andrew Howroyd, Jan 15 2020

Keywords

Comments

The condition that the rows be in nonincreasing order is equivalent to considering nonequivalent matrices up to permutation of rows.
a(n) is the number of T_0 3-regular set multipartitions (multisets of sets) on an n-set.

Examples

			The a(2) = 3 matrices are:
   [1 0]   [1 1]   [1 1]
   [1 0]   [1 0]   [1 1]
   [1 0]   [1 0]   [1 0]
   [0 1]   [0 1]   [0 1]
   [0 1]   [0 1]
   [0 1]
		

Crossrefs

Row n=3 of A331126.
Cf. A165434.

Formula

a(n) = Sum_{k=0..n} Stirling1(n,k)*A165434(k). - Andrew Howroyd, Jan 31 2020

A165437 The number of six-fold coverings of a set.

Original entry on oeis.org

1, 1, 7, 256, 52450, 46757209, 135029200594, 992649275638900, 15637211080656145509, 468371757818481922636261, 24491541042280069722306974244, 2097907014780540445950132842480077, 280173584370772226399860619059838944713, 56066456120812871209756615894736908159099853
Offset: 0

Views

Author

Doron Zeilberger, Sep 18 2009

Keywords

Comments

Analogous to A165434. See comments and references there.

Crossrefs

Row n=6 of A188392.
Cf. A165434.

Extensions

a(11)-a(13) from Andrew Howroyd, Dec 10 2018
Showing 1-8 of 8 results.