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 A378225 #7 Nov 25 2024 13:30:54
%S A378225 1,-2,-2,0,-2,2,-2,0,0,2,-2,0,-2,2,2,0,-2,0,-2,0,2,2,-2,0,0,2,0,0,-2,
%T A378225 -2,-2,0,2,2,2,0,-2,2,2,0,-2,-2,-2,0,0,2,-2,0,0,0,2,0,-2,0,2,0,2,2,-2,
%U A378225 0,-2,2,0,0,2,-2,-2,0,2,-2,-2,0,-2,2,0,0,2,-2,-2,0,0,2,-2,0,2,2,2,0,-2,0,2,0,2,2,2,0,-2
%N A378225 Dirichlet inverse of A067824.
%C A378225 Möbius transform of A153881.
%H A378225 Antti Karttunen, <a href="/A378225/b378225.txt">Table of n, a(n) for n = 1..20000</a>
%F A378225 a(1) = 1, and for n > 1, a(n) = -Sum_{d|n, d<n} A067824(n/d) * a(d).
%F A378225 a(n) = Sum_{d|n} A008683(n/d)*A153881(d).
%F A378225 Dirichlet g.f.: (2 - zeta(s)) / zeta(s). [See Dec 30 2018 formula in A067824]
%o A378225 (PARI)
%o A378225 A074206(n) = if(n>1, sumdiv(n, i, if(i<n, A074206(i))), n); \\ From A074206
%o A378225 A067824(n) = sumdiv(n,d,A074206(d));
%o A378225 memoA378225 = Map();
%o A378225 A378225(n) = if(1==n,1,my(v); if(mapisdefined(memoA378225,n,&v), v, v = -sumdiv(n,d,if(d<n,A067824(n/d)*A378225(d),0)); mapput(memoA378225,n,v); (v)));
%Y A378225 Cf. A008683, A067824, A153881.
%Y A378225 Cf. also A378224.
%K A378225 sign
%O A378225 1,2
%A A378225 _Antti Karttunen_, Nov 25 2024