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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.

A077014 Number of ways that a directed line (or river) that starts in the south can cross an east-west road n times.

Table of values

n a(n)
0 2
1 1
2 2
3 2
4 6
5 8
6 28
7 42
8 162
9 262
10 1076
11 1828
12 7852
13 13820
14 61388
15 110954
16 505878
17 933458
18 4345660
19 8152860
20 38608380
21 73424650
22 352686780
23 678390116
24 3298016912
25 6405031050
26 31461151108
27 61606881612
28 305327366988
29 602188541928
30 3007925909860
31 5969806669034

List of values

[2, 1, 2, 2, 6, 8, 28, 42, 162, 262, 1076, 1828, 7852, 13820, 61388, 110954, 505878, 933458, 4345660, 8152860, 38608380, 73424650, 352686780, 678390116, 3298016912, 6405031050, 31461151108, 61606881612, 305327366988, 602188541928, 3007925909860, 5969806669034]

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

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