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.
%I A107647 #21 Oct 24 2023 08:05:35
%S A107647 1,1,1,2,6,12,8,20,54,148,136,144,612,1200,1344,2448,10506,16848,
%T A107647 13824,22000,83232,148716,205368,377736,920160,1694088,1880304,
%U A107647 3290112,14839968,22472640,17805312,42407136,117876096,327661128,178588800,561863168,1604383200
%N A107647 Euler's totient function applied to tribonacci numbers.
%H A107647 Amiram Eldar, <a href="/A107647/b107647.txt">Table of n, a(n) for n = 2..365</a>
%F A107647 a(n) = A000010(A000073(n)). - _Amiram Eldar_, Mar 02 2020
%t A107647 F[1] = 0; F[2] = 1; F[3] = 1; F[n__] := F[n] = F[n - 1] + F[n - 2] + F[n - 3]; Table[EulerPhi[F[n]], {n, 2, 50}]
%Y A107647 Cf. A000010, A000073, A065449, A197218, A272040.
%K A107647 nonn
%O A107647 2,4
%A A107647 _Roger L. Bagula_, Jun 09 2005
%E A107647 First term 0 removed and offset corrected by _Amiram Eldar_, Mar 02 2020