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.

A187981 Number of nondecreasing arrangements of n numbers x(i) in -n..n with the sum of sign(x(i))*2^|x(i)| zero.

Table of values

n a(n)
1 0
2 2
3 5
4 15
5 57
6 181
7 632
8 2199
9 7593
10 26706
11 93724
12 330555
13 1170088
14 4149361
15 14754670
16 52564714
17 187595025
18 670589799
19 2400467901
20 8603906865
21 30874479617
22 110907636467
23 398789645747
24 1435195800184
25 5169318396770
26 18633022691923
27 67210498566801
28 242590233305619
29 876138147816208
30 3166048659124955
31 11447024096561941
32 41407915745717488

List of values

[0, 2, 5, 15, 57, 181, 632, 2199, 7593, 26706, 93724, 330555, 1170088, 4149361, 14754670, 52564714, 187595025, 670589799, 2400467901, 8603906865, 30874479617, 110907636467, 398789645747, 1435195800184, 5169318396770, 18633022691923, 67210498566801, 242590233305619, 876138147816208, 3166048659124955, 11447024096561941, 41407915745717488]

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

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