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