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 A350521 #26 Apr 11 2024 17:22:00
%S A350521 4,22,40,58,76,94,112,130,148,166,184,202,220,238,256,274,292,310,328,
%T A350521 346,364,382,400,418,436,454,472,490,508,526,544,562,580,598,616,634,
%U A350521 652,670,688,706,724,742,760,778,796,814,832,850,868,886,904,922,940,958
%N A350521 a(n) = 18*n + 4.
%C A350521 Second column of A006370 (the Collatz or 3x+1 map) when it is interpreted as a rectangular array with six columns read by rows.
%H A350521 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).
%F A350521 a(n) = A242215(n) - 1.
%F A350521 a(n) = A298035(n+1) + 1.
%F A350521 From _Elmo R. Oliveira_, Apr 08 2024: (Start)
%F A350521 G.f.: 2*(2+7*x)/(1-x)^2.
%F A350521 E.g.f.: 2*exp(x)*(2 + 9*x).
%F A350521 a(n) = 2*a(n-1) - a(n-2) for n >= 2.
%F A350521 a(n) = 2*A017185(n) = A006370(A016921(n)). (End)
%p A350521 seq(18*n+4, n=0..53);
%t A350521 Table[18n+4, {n, 0, 53}]
%o A350521 (PARI) a(n)=18*n+4
%o A350521 (Magma) [18*n+4: n in [0..53]];
%o A350521 (Maxima) makelist(18*n+4, n, 0, 53);
%o A350521 (GAP) List([0..53], n-> 18*n+4)
%o A350521 (Python) [18*n+4 for n in range(53)]
%Y A350521 Bisection of A017209.
%Y A350521 Cf. A006370, A008600, A016921, A017185, A242215, A298035.
%K A350521 nonn,easy
%O A350521 0,1
%A A350521 _Omar E. Pol_, Jan 03 2022