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 A003981 #18 Sep 04 2023 02:01:53
%S A003981 1,3,4,7,6,12,9,15,13,18,14,28,22,27,24,31,35,39,56,42,36,42,90,60,31,
%T A003981 66,40,63,145,72,234,63,56,105,54,91,378,168,88,90,611,108,988,98,78,
%U A003981 270,1598,124,73,93,140,154,2585,120,84,135,224,435,4182,168,6766,702
%N A003981 Inverse Möbius transform of A003965.
%H A003981 N. J. A. Sloane, <a href="/transforms.txt">Transforms</a>.
%F A003981 Multiplicative with a(p^e) = (q^(e+1)-1)/(q-1) where q = Fibonacci(pi(p)+1) = A000045(A000720(p)+2). - _David W. Wilson_, Sep 01 2001
%t A003981 f[p_, e_] := Module[{q = Fibonacci[PrimePi[p] + 2]}, (q^(e+1)-1)/(q-1)]; a[n_] := Times @@ f @@@ FactorInteger[n]; a[1] = 1; Array[a, 100] (* _Amiram Eldar_, Sep 04 2023 *)
%Y A003981 Cf. A000045, A000720, A003965.
%K A003981 nonn,easy,mult
%O A003981 1,2
%A A003981 _Marc LeBrun_
%E A003981 More terms from _David W. Wilson_, Aug 29 2001