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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.

A195639 Number of lower triangles of an n X n 0..3 array with all row sums equal to the length of the row and all column sums equal to the length of the column.

Table of values

n a(n)
1 1
2 1
3 3
4 19
5 379
6 22506
7 4063437
8 2303397986
9 4165684145897
10 24351094470461293
11 465231630106636264261
12 29310412705455253400706632
13 6135104108066245513806738233622
14 4293669524764808720927311131475805624
15 10102086274414407316013385512463577654333437

List of values

[1, 1, 3, 19, 379, 22506, 4063437, 2303397986, 4165684145897, 24351094470461293, 465231630106636264261, 29310412705455253400706632, 6135104108066245513806738233622, 4293669524764808720927311131475805624, 10102086274414407316013385512463577654333437]

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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