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.

A346426 Number A(n,k) of partitions of the (n+k)-multiset {0,...,0,1,2,...,k} with n 0's; square array A(n,k), n>=0, k>=0, read by antidiagonals.

Original entry on oeis.org

1, 1, 1, 2, 2, 2, 5, 5, 4, 3, 15, 15, 11, 7, 5, 52, 52, 36, 21, 12, 7, 203, 203, 135, 74, 38, 19, 11, 877, 877, 566, 296, 141, 64, 30, 15, 4140, 4140, 2610, 1315, 592, 250, 105, 45, 22, 21147, 21147, 13082, 6393, 2752, 1098, 426, 165, 67, 30, 115975, 115975, 70631, 33645, 13960, 5317, 1940, 696, 254, 97, 42
Offset: 0

Views

Author

Alois P. Heinz, Jul 16 2021

Keywords

Comments

Also number A(n,k) of factorizations of 2^n * Product_{i=1..k} prime(i+1); A(3,1) = 7: 2*2*2*3, 2*3*4, 4*6, 2*2*6, 3*8, 2*12, 24; A(1,2) = 5: 2*3*5, 5*6, 3*10, 2*15, 30.

Examples

			A(2,2) = 11: 00|1|2, 001|2, 1|002, 0|0|1|2, 0|01|2, 0|1|02, 01|02, 00|12, 0|0|12, 0|012, 0012.
Square array A(n,k) begins:
   1,  1,   2,    5,   15,    52,    203,     877,    4140, ...
   1,  2,   5,   15,   52,   203,    877,    4140,   21147, ...
   2,  4,  11,   36,  135,   566,   2610,   13082,   70631, ...
   3,  7,  21,   74,  296,  1315,   6393,   33645,  190085, ...
   5, 12,  38,  141,  592,  2752,  13960,   76464,  448603, ...
   7, 19,  64,  250, 1098,  5317,  28009,  158926,  963913, ...
  11, 30, 105,  426, 1940,  9722,  52902,  309546, 1933171, ...
  15, 45, 165,  696, 3281, 16972,  95129,  572402, 3670878, ...
  22, 67, 254, 1106, 5372, 28582, 164528, 1015356, 6670707, ...
  ...
		

Crossrefs

Programs

  • Maple
    s:= proc(n) option remember; expand(`if`(n=0, 1,
          x*add(s(n-j)*binomial(n-1, j-1), j=1..n)))
        end:
    S:= proc(n, k) option remember; coeff(s(n), x, k) end:
    b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i=0,
          combinat[numbpart](n), add(b(n-j, i-1), j=0..n)))
        end:
    A:= (n, k)-> add(S(k, j)*b(n, j), j=0..k):
    seq(seq(A(n, d-n), n=0..d), d=0..10);
  • Mathematica
    s[n_] := s[n] = Expand[If[n == 0, 1, x Sum[s[n - j] Binomial[n - 1, j - 1], {j, 1, n}]]];
    S[n_, k_] := S[n, k] = Coefficient[s[n], x, k];
    b[n_, i_] := b[n, i] = If[n == 0, 1, If[i == 0, PartitionsP[n], Sum[b[n - j, i - 1], {j, 0, n}]]];
    A[n_, k_] := Sum[S[k, j] b[n, j], {j, 0, k}];
    Table[Table[A[n, d - n], {n, 0, d}], {d, 0, 10}] // Flatten (* Jean-François Alcover, Aug 18 2021, after Alois P. Heinz *)

Formula

A(n,k) = A001055(A000079(n)*A070826(k+1)).
A(n,k) = Sum_{j=0..k} A048993(k,j)*A292508(n,j+1).
A(n,k) = Sum_{j=0..k} Stirling2(k,j)*Sum_{i=0..n} binomial(j+i-1,i)*A000041(n-i).

A129306 Resort sequence A096443 by source partition as described by A053445 and A126442.

Original entry on oeis.org

1, 2, 2, 3, 4, 5, 5, 7, 11, 15, 9, 7, 12, 21, 36, 52, 16, 26, 11, 19, 38, 74, 135, 203, 29, 52, 92, 31, 66, 15, 30, 64, 141, 296, 566, 877, 47, 98, 198, 371, 57, 109, 137, 249, 22, 45, 105, 250, 592, 1315, 2610, 4140, 77, 171, 392, 850, 1663, 97, 212, 444, 269, 560, 1075
Offset: 1

Views

Author

Alford Arnold, May 07 2007

Keywords

Comments

The first array is described in A126442 and is the hook case. Sequence A129305 encodes the multisets counted by A096443 and A129306.

Examples

			a(11) = 9 because 2+2= 4 starting a new array. The arrays begin as follows:
1.....2.....3.....5......7......11.....15.....22
......2.....4.....7......12.....19.....30.....45
............5.....11.....21.....38.....64.....105
..................15.....36.....74.....141....250
.........................52.....135....296....592
................................203....566....1315
.......................................877....2610
..............................................4140
..................9......16.....29.....47.....77
.........................26.....52.....98.....171
................................92.....198....392
.......................................371....850
..............................................1663
................................31.....57.....97
.......................................109....212
..............................................444
................................66.....137....269
.......................................249....560
..............................................1075
..............................................109
..............................................300
..............................................712
which sums to
1.....4....12....47....170....750....3255.....16010
		

Crossrefs

A126442 Triangular array t read by rows: t(0,k) is p(k), the number of partitions of the k-multiset {0,0,...,0} with k zeros. For 0 <= n < k, t(n, k) is the number of partitions of the k-multiset {0, 0, ..., 0, 1, 2, 3, ..., k-n} with n zeros.

Original entry on oeis.org

1, 2, 2, 3, 4, 5, 5, 7, 11, 15, 7, 12, 21, 36, 52, 11, 19, 38, 74, 135, 203, 15, 30, 64, 141, 296, 566, 877, 22, 45, 105, 250, 592, 1315, 2610, 4140, 30, 67, 165, 426, 1098, 2752, 6393, 13082, 21147, 42, 97, 254, 696, 1940, 5317, 13960, 33645, 70631, 115975
Offset: 1

Views

Author

Alford Arnold, Jan 28 2007

Keywords

Comments

First in a series of triangular arrays which comprise subsequences of A096443(n).
The second array begins 9 16 26 29 52 92 47 98 198 371 and when the arrays are aligned as illustrated in triangle A126441 with p(n) values they sum to A035310 which counts unordered multisets.
Let t(n, k) be the number of ways to partition the k-multiset {0,0,...,0,1,2,3,4,...,k-n} with n zeros, 0 <= n < k. Then t(n, k) = sum_i = 0..k j = 0..n S(n, j) C(i, j) p(k - n - i), where S(n, j) are Stirling numbers of the second kind, C(i, j) are the number of compositions of i distinct objects into j parts, and p is the integer partition function.
To see this, partition [n] into j blocks; there are S(n, j) partitions. For such a partition x and for each i, there are C(i, j) ways to distribute i zeros into x, because the blocks of x are all distinct. There are p(k-n-i) ways to partition the remaining k-n-i zeros. Multiplying and summing gives the result. - George Beck, Jan 10 2011
Values are also part of A096443, A129306 and A249620. Columns are also columns of the last one of these irregular triangles. See "Partitions_of_multisets" link. - Tilman Piesk, Nov 09 2014

Examples

			This first array includes only the hook cases. A096443(9,14,16) correspond to partitions [2,2], [3,2] and [2,2,1] so these values do not appear in A126442.
The array begins:
1
2 2
3 4 5
5 7 11 15
7 12 21 36 52
		

Crossrefs

Programs

  • Mathematica
    (* The triangle is flattened to a sequence. *)
    t[n_, k_] := Sum[StirlingS2[n, j] * Binomial[-1 + i + j, i] * PartitionsP[k - n - i], {j, 0, n}, {i, 0, k - n}]; Table[ t[n, k], {k, 10}, {n, 0, k - 1}] // Flatten (* George Beck, Jan 10 2011 *)

Extensions

Definition clarified by George Beck, Jan 11 2011

A002763 Number of bipartite partitions.

Original entry on oeis.org

4, 11, 26, 52, 98, 171, 289, 467, 737, 1131, 1704, 2515, 3661, 5246, 7430, 10396, 14405, 19760, 26884, 36269, 48583, 64614, 85399, 112170, 146526, 190362, 246099, 316621, 405556, 517224, 657012, 831320, 1048055, 1316611, 1648486, 2057324, 2559719, 3175309
Offset: 0

Views

Author

Keywords

References

  • M. S. Cheema and H. Gupta, Tables of Partitions of Gaussian Integers. National Institute of Sciences of India, Mathematical Tables, Vol. 1, New Delhi, 1956, p. 11.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Programs

  • Maple
    with(numtheory):
    b:= proc(n, k) option remember;
          `if`(n>k, 0, 1) +`if`(isprime(n), 0,
          add(`if`(d>k, 0, b(n/d, d)), d=divisors(n) minus {1, n}))
        end:
    a:= n-> b((45*2^n)$2):
    seq(a(n), n=0..50);  # Alois P. Heinz, May 26 2013
  • Mathematica
    b[n_, k_] := b[n, k] = If[n>k, 0, 1] + If[PrimeQ[n], 0, Sum[If[d>k, 0, b[n/d, d]], {d, DeleteCases[Divisors[n], 1|n]}]]; a[n_] := b[45*2^n, 45*2^n]; Table[a[n], {n, 0, 50}] (* Jean-François Alcover, Mar 20 2014, after Alois P. Heinz *)
    nmax = 100; CoefficientList[Series[(4 - x - 3*x^2 + x^3) / ((1 - x)^3 * (1 + x)) / Product[1 - x^k, {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Jan 07 2017 *)

Formula

a(n) = a(n-1) + A000041(n) + A000070(n) + A000291(n), for n>0 - Alford Arnold, Dec 10 2007
From Vaclav Kotesovec, Jan 07 2017: (Start)
G.f.: (4 - x - 3*x^2 + x^3) / ((1-x)^3 * (1+x)) * Product_{k>=1} 1/(1-x^k).
a(n) ~ exp(Pi*sqrt(2*n/3)) * 3*sqrt(n)/(2*sqrt(2)*Pi^3).
(End)

Extensions

Extended beyond a(25) by Alois P. Heinz, May 26 2013

A346822 Number of partitions of the (n+2)-multiset {0,...,0,1,2} with n 0's into distinct multisets.

Original entry on oeis.org

2, 5, 9, 16, 25, 38, 56, 80, 111, 152, 205, 272, 357, 463, 595, 759, 960, 1205, 1504, 1865, 2300, 2823, 3448, 4192, 5076, 6122, 7356, 8809, 10514, 12509, 14840, 17555, 20710, 24371, 28608, 33503, 39149, 45647, 53113, 61679, 71489, 82706, 95515, 110118, 126743
Offset: 0

Views

Author

Alois P. Heinz, Aug 05 2021

Keywords

Comments

Also number of factorizations of 2^n * 15 into distinct factors.

Crossrefs

Column k=2 of A346520.
Cf. A082775.
Showing 1-5 of 5 results.