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 A378986 #10 Dec 14 2024 11:01:00
%S A378986 0,0,-2,0,-2,-4,-2,0,-6,-4,-2,-8,-2,-4,-14,0,-2,-12,-2,-8,-18,-4,-2,
%T A378986 -16,-10,-4,-18,-8,-2,-28,-2,0,-26,-4,-22,-24,-2,-4,-30,-16,-2,-36,-2,
%U A378986 -8,-42,-4,-2,-32,-14,-20,-38,-8,-2,-36,-30,-16,-42,-4,-2,-56,-2,-4,-54,0,-34,-52,-2,-8,-50,-44,-2,-48,-2,-4
%N A378986 a(n) = 2*phi(2*n) - 2*n, where phi is Euler totient function.
%H A378986 Antti Karttunen, <a href="/A378986/b378986.txt">Table of n, a(n) for n = 1..32769</a>
%F A378986 a(n) = 2*A000010(2*n) - 2*n.
%F A378986 a(n) = A083254(2*n) = A297114(2*n).
%F A378986 a(n) = -2*A176095(n).
%F A378986 a(n) = Sum_{d|2n} A008683(d)*A033879(2*n/d).
%o A378986 (PARI) A378986(n) = (2*eulerphi(2*n)-(2*n));
%Y A378986 Even bisection of A083254, and of A297114.
%Y A378986 First row of A379011.
%Y A378986 Cf. A000010, A008683, A033879, A062570, A176095, A378978.
%Y A378986 Cf. also A378987.
%K A378986 sign
%O A378986 1,3
%A A378986 _Antti Karttunen_, Dec 14 2024