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.

A375924 Number A(n,k) of partitions of [n] such that the element sum of each block is one more than a multiple of k; square array A(n,k), n>=0, k>=0, read by antidiagonals.

Original entry on oeis.org

1, 1, 1, 1, 1, 0, 1, 1, 2, 0, 1, 1, 1, 5, 0, 1, 1, 0, 2, 15, 0, 1, 1, 0, 0, 4, 52, 0, 1, 1, 0, 1, 1, 10, 203, 0, 1, 1, 0, 1, 2, 3, 28, 877, 0, 1, 1, 0, 0, 0, 3, 9, 96, 4140, 0, 1, 1, 0, 0, 0, 0, 1, 17, 320, 21147, 0, 1, 1, 0, 0, 0, 1, 1, 8, 108, 1436, 115975, 0
Offset: 0

Views

Author

Alois P. Heinz, Sep 02 2024

Keywords

Examples

			A(5,2) = 10: 12345, 124|3|5, 12|34|5, 12|3|45, 14|23|5, 1|234|5, 1|23|45, 14|25|3, 1|245|3, 1|25|34.
A(6,3) = 9: 136|25|4, 13|256|4, 13|25|46, 16|235|4, 1|2356|4, 1|235|46, 16|25|34, 1|256|34, 1|25|346.
A(7,4) = 8: 14|23|5|67, 1|234|5|67, 1|23|45|67, 1|23|467|5, 14|27|36|5, 1|247|36|5, 1|27|346|5, 1|27|36|45.
A(8,5) = 1: 12345678.
A(8,8) = 4: 18|27|36|45, 1|278|36|45, 1|27|368|45, 1|27|36|458.
A(9,6) = 87: 123469|58|7, 12349|568|7, 12349|58|67, 123568|49|7, ..., 1|25|346789, 16|289|3457, 1|2689|3457, 1|289|34567.
A(9,8) = 5: 18|27|36|45|9, 1|278|36|45|9, 1|27|368|45|9, 1|27|36|458|9, 1|27|36|45|89.
A(9,10) = 1: 1|29|38|47|56.
Square array A(n,k) begins:
  1,      1,    1,    1,   1,  1,  1,  1, 1, 1, 1, ...
  1,      1,    1,    1,   1,  1,  1,  1, 1, 1, 1, ...
  0,      2,    1,    0,   0,  0,  0,  0, 0, 0, 0, ...
  0,      5,    2,    0,   1,  1,  0,  0, 0, 0, 0, ...
  0,     15,    4,    1,   2,  0,  0,  0, 1, 1, 0, ...
  0,     52,   10,    3,   3,  0,  1,  1, 0, 0, 0, ...
  0,    203,   28,    9,   1,  1,  3,  0, 0, 1, 1, ...
  0,    877,   96,   17,   8, 15,  4,  0, 1, 1, 0, ...
  0,   4140,  320,  108,  32,  1,  0,  1, 4, 0, 0, ...
  0,  21147, 1436,  324,  51, 10, 87, 72, 5, 0, 1, ...
  0, 115975, 5556, 1409, 621, 50,  1,  0, 0, 1, 5, ...
		

Crossrefs

Rows n=1-2 give: A000012, A033322 (for k>=1).
Main diagonal gives A142150 (for n>=2).
A(n+1,n) gives A158416 (for n>=2).
A(n,n+1) gives A135528(n+1).

A374692 Number of partitions of [n] such that the element sum of each block is one more than a multiple of three.

Original entry on oeis.org

1, 1, 0, 0, 1, 3, 9, 17, 108, 324, 1409, 3807, 13365, 105764, 347976, 1825416, 11309203, 76330674, 453496320, 2638063039, 19573857765, 121970492469, 939636604957, 5944482289926, 41069772211068, 388012765239587, 2642662404898875, 21056674779654003
Offset: 0

Views

Author

Alois P. Heinz, Aug 31 2024

Keywords

Examples

			a(0) = 1: the empty partition.
a(1) = 1: 1.
a(4) = 1: 1234.
a(5) = 3: 13|25|4, 1|235|4, 1|25|34.
a(6) = 9: 136|25|4, 13|256|4, 13|25|46, 16|235|4, 1|2356|4, 1|235|46, 16|25|34, 1|256|34, 1|25|346.
a(7) = 17: 1234567, 136|25|4|7, 13|256|4|7, 13|25|46|7, 13|25|4|67, 16|235|4|7, 1|2356|4|7, 1|235|46|7, 1|235|4|67, 16|25|34|7, 1|256|34|7, 1|25|346|7, 1|25|34|67, 16|25|37|4, 1|256|37|4, 1|25|367|4, 1|25|37|46.
		

Crossrefs

Column k=3 of A375924.
Cf. A369079.

A369080 Number of permutations of [n] such that the element sum of each cycle is odd.

Original entry on oeis.org

1, 1, 1, 2, 6, 36, 180, 1080, 7560, 75600, 680400, 6804000, 74844000, 1047816000, 13621608000, 190702512000, 2860537680000, 51489678240000, 875324530080000, 15755841541440000, 299360989287360000, 6585941764321920000, 138304777050760320000, 3042705095116727040000
Offset: 0

Views

Author

Alois P. Heinz, Jan 12 2024

Keywords

Comments

Number of permutations of [n] such that each cycle has an odd number of odd elements.
a(n+1)/a(n) is an integer for all n >= 0.

Examples

			a(0) = 1: the empty permutation.
a(1) = 1: (1).
a(2) = 1: (12).
a(3) = 2: (12)(3), (1)(23).
a(4) = 6: (124)(3), (142)(3), (12)(34), (14)(23), (1)(234), (1)(243).
		

Crossrefs

Programs

  • Maple
    b:= proc(x, y) option remember; `if`(x+y=0, 1, add(
          `if`(j::odd, binomial(x-1, j-1)*add((i+j-1)!*
           b(x-j, y-i)*binomial(y, i), i=0..y), 0), j=1..x))
        end:
    a:= n-> (h-> b(n-h, h))(iquo(n, 2)):
    seq(a(n), n=0..23);
    # second Maple program:
    b:= n-> (<<0|1|0|0|0>, <0|0|1|0|0>, <0|0|0|1|0>,
              <0|0|0|0|1>, <-1|1|0|0|1>>^n. <<1, 2, 3, 6, 5>>)[1, 1]:
    a:= proc(n) option remember; `if`(n<2, 1, a(n-1)*b(n-2)) end:
    seq(a(n), n=0..23);

A375099 Number of partitions of [n] into blocks whose element sum is <= n.

Original entry on oeis.org

1, 1, 1, 2, 3, 6, 12, 26, 57, 141, 333, 885, 2259, 6391, 17302, 51685, 147937, 460561, 1389093, 4504136, 14127767, 47719998, 155559696, 542178148, 1835105103, 6600158865, 23035501468, 85428655084, 307266398440, 1168951871972, 4331125790382, 16897269822235
Offset: 0

Views

Author

Alois P. Heinz, Jul 29 2024

Keywords

Examples

			a(0) = 1: the empty partition.
a(1) = 1: 1.
a(2) = 1: 1|2.
a(3) = 2: 12|3, 1|2|3.
a(4) = 3: 12|3|4, 13|2|4, 1|2|3|4.
a(5) = 6: 12|3|4|5, 13|2|4|5, 14|23|5, 1|23|4|5, 14|2|3|5, 1|2|3|4|5.
a(6) = 12: 123|4|5|6, 12|3|4|5|6, 13|24|5|6, 13|2|4|5|6, 14|23|5|6, 15|23|4|6, 1|23|4|5|6, 14|2|3|5|6, 15|24|3|6, 1|24|3|5|6, 15|2|3|4|6, 1|2|3|4|5|6.
		

Crossrefs

Main diagonal of A374932.
Row sums of A375023.
Showing 1-4 of 4 results.