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.

A277236 Number of strings of length n composed of symbols from the circular list [1,2,3,4] such that adjacent symbols in the string must be adjacent in the list. No runs of length 2 or more are allowed for symbols 1 and 3.

Table of values

n a(n)
0 1
1 4
2 10
3 26
4 66
5 170
6 434
7 1114
8 2850
9 7306
10 18706
11 47930
12 122754
13 314474
14 805490
15 2063386
16 5285346
17 13538890
18 34680274
19 88835834
20 227556930
21 582900266
22 1493127986
23 3824729050
24 9797240994
25 25096157194
26 64285121170
27 164669749946
28 421810234626
29 1080489234410
30 2767730172914

List of values

[1, 4, 10, 26, 66, 170, 434, 1114, 2850, 7306, 18706, 47930, 122754, 314474, 805490, 2063386, 5285346, 13538890, 34680274, 88835834, 227556930, 582900266, 1493127986, 3824729050, 9797240994, 25096157194, 64285121170, 164669749946, 421810234626, 1080489234410, 2767730172914]

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

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