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.

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A050913 Pure 2-complexes on an infinite set of nodes with n multiple 2-simplexes. Also n-rowed binary matrices with all row sums 3, up to row and column permutation.

Original entry on oeis.org

1, 1, 4, 16, 93, 652, 6369, 79568, 1256425, 24058631, 543204998, 14138916124, 417362929209, 13798729189578, 505990335048034, 20415765544541866, 900364519682003919, 43155049922002494115, 2236988329443856718604, 124862936181977439454012, 7476052709321753156375756, 478506183522725779096476581, 32638841238874891261354722405, 2365895836144423508306322639848, 181785988254681334224483607437510, 14771116583797935886529061991645404, 1266545494725474774697216198539818982
Offset: 0

Views

Author

Vladeta Jovovic, Dec 29 1999

Keywords

Links

Crossrefs

Row n=3 of A331461.
Cf. A050911, A050912, A001400, A014395, A082789, A082790, A058790.

Extensions

More terms from T. Forbes (anthony.d.forbes(AT)googlemail.com), May 24 2003

A305027 Array read by antidiagonals: T(n,m) is the number of nonisomorphic binary n X m matrices with 3 1's per column under row and column permutations (m >= 3).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 3, 3, 1, 1, 1, 4, 7, 5, 1, 1, 1, 4, 11, 17, 6, 1, 1, 1, 4, 14, 40, 35, 9, 1, 1, 1, 4, 15, 62, 122, 76, 11, 1, 1, 1, 4, 16, 78, 272, 410, 149, 15, 1, 1, 1, 4, 16, 87, 427, 1307, 1270, 291, 18, 1, 1, 1, 4, 16, 91, 544, 2754, 6178, 3888, 539, 23, 1
Offset: 0

Views

Author

Andrew Howroyd, May 24 2018

Keywords

Comments

Also, the number of pure 2-complexes on m nodes with n multiple 2-simplexes.

Examples

			Array begins:
========================================================
n\m| 3  4   5    6     7      8      9     10     11
---+----------------------------------------------------
0  | 1  1   1    1     1      1      1      1      1 ...
1  | 1  1   1    1     1      1      1      1      1 ...
2  | 1  2   3    4     4      4      4      4      4 ...
3  | 1  3   7   11    14     15     16     16     16 ...
4  | 1  5  17   40    62     78     87     91     92 ...
5  | 1  6  35  122   272    427    544    606    635 ...
6  | 1  9  76  410  1307   2754   4251   5343   5939 ...
7  | 1 11 149 1270  6178  18247  36455  54621  67609 ...
8  | 1 15 291 3888 28687 122038 327774 616020 891831 ...
...

Links

Crossrefs

Columns m=4..7 are A001400, A014395, A050911, A050912.
A diagonal is A247596.
Cf. A050913 (infinite m), A304942.

Programs

  • PARI
    \\ See A304942 for Blocks
for(n=1, 8, for(m=3, 11, print1(Blocks(n, m, 3), ", ")); print)
Showing 1-2 of 2 results.

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