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 A375966 #34 Sep 24 2024 14:52:58
%S A375966 1,1,3,4,9,16,27,64,81,256,243,1024,729,4096,2187,16384,6561,65536,
%T A375966 19683,262144,59049,1048576,177147,4194304,531441,16777216,1594323,
%U A375966 67108864,4782969,268435456,14348907,1073741824,43046721,4294967296,129140163,17179869184
%N A375966 Powers of 3 alternating with powers of 4.
%H A375966 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,7,0,-12).
%F A375966 a(n) = 7*a(n-2) - 12*a(n-4) for n >= 4.
%F A375966 From _Stefano Spezia_, Sep 06 2024: (Start)
%F A375966 G.f.: (1 + x - 4*x^2 - 3*x^3)/((1 - 2*x)*(1 + 2*x)*(1 - 3*x^2)).
%F A375966 a(n) = (4*3^(n/2)*A059841(n) - (-2)^n + 2^n)/4.
%F A375966 E.g.f.: cosh(sqrt(3)*x) + cosh(x)*sinh(x). (End)
%t A375966 seq[len_] := Module[{m = Ceiling[len/2] - 1}, Riffle @@ Map[#^Range[0, m] &, {3, 4}]]; seq[36] (* _Amiram Eldar_, Sep 05 2024 *)
%o A375966 (Python)
%o A375966 def A375966(n): return 1<<(n^1) if n&1 else 3**(n>>1) # _Chai Wah Wu_, Sep 24 2024
%Y A375966 Cf. A000244 and A000302 interleaved.
%Y A375966 Cf. A000035, A059841, A072345, A098293.
%K A375966 nonn,easy
%O A375966 0,3
%A A375966 _Paul Curtz_, Sep 04 2024