A350521 - OEIS

%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