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 A357238 #7 Sep 23 2022 03:20:41
%S A357238 0,1,1,3,4,9,13,27,45,86,149,285,504,941,1710,3163,5768,10662,19513,
%T A357238 35978,66026,121565,223317,411053,755480,1390042,2555802,4701713,
%U A357238 8646064,15904390,29249425,53801243,98950246,182003370,334745794,615704412,1132436852,2082895617,3831006934
%N A357238 Inverse Moebius transform of tribonacci numbers (A000073).
%F A357238 G.f.: Sum_{k>=1} x^(2*k) / (1 - x^k - x^(2*k) - x^(3*k)).
%F A357238 G.f.: Sum_{k>=1} A000073(k) * x^k / (1 - x^k).
%F A357238 a(n) = Sum_{d|n} A000073(d).
%t A357238 nmax = 39; CoefficientList[Series[Sum[x^(2 k)/(1 - x^k - x^(2 k) - x^(3 k)), {k, 1, nmax}], {x, 0, nmax}], x] // Rest
%o A357238 (PARI) f(n) = ([0, 1, 0; 0, 0, 1; 1, 1, 1]^n)[1, 3]; \\ A000073
%o A357238 a(n) = sumdiv(n, d, f(d)); \\ _Michel Marcus_, Sep 20 2022
%Y A357238 Cf. A000073, A007435, A357239.
%K A357238 nonn
%O A357238 1,4
%A A357238 _Ilya Gutkovskiy_, Sep 19 2022