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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.

A306988 a(n) = Sum_{k=1..n} binomial(n,k)*phi(k), where phi is the Euler totient function.

Table of values

n a(n)
1 1
2 3
3 8
4 20
5 49
6 117
7 272
8 620
9 1395
10 3107
11 6852
12 14964
13 32395
14 69647
15 149002
16 317712
17 675749
18 1433769
19 3033444
20 6396320
21 13437913
22 28130869
23 58708304
24 122239396
25 254141275
26 527946013
27 1096312050
28 2275897660
29 4722500707
30 9791471587
31 20277706762
32 41932520528

List of values

[1, 3, 8, 20, 49, 117, 272, 620, 1395, 3107, 6852, 14964, 32395, 69647, 149002, 317712, 675749, 1433769, 3033444, 6396320, 13437913, 28130869, 58708304, 122239396, 254141275, 527946013, 1096312050, 2275897660, 4722500707, 9791471587, 20277706762, 41932520528]

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

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