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.

A064821 Number of ways of writing the numbers 1 .. n in a sequence so that the sum of any two adjacent numbers is a prime; reversing the sequence does not count as different.

Table of values

n a(n)
1 0
2 1
3 1
4 4
5 2
6 8
7 12
8 30
9 70
10 664
11 1072
12 8768
13 11648
14 37108
15 95772
16 1059816
17 2047488
18 12111712
19 22802028
20 120779959
21 337801784
22 4361743860
23 11425028900
24 142573286216
25 429917269469
26 4138239848098
27 16171519847028
28 214845911686065

List of values

[0, 1, 1, 4, 2, 8, 12, 30, 70, 664, 1072, 8768, 11648, 37108, 95772, 1059816, 2047488, 12111712, 22802028, 120779959, 337801784, 4361743860, 11425028900, 142573286216, 429917269469, 4138239848098, 16171519847028, 214845911686065]

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

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