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 A066043 #23 Feb 19 2024 03:32:46
%S A066043 1,2,6,4,10,6,14,8,18,10,22,12,26,14,30,16,34,18,38,20,42,22,46,24,50,
%T A066043 26,54,28,58,30,62,32,66,34,70,36,74,38,78,40,82,42,86,44,90,46,94,48,
%U A066043 98,50,102,52,106,54,110,56,114,58,118,60,122,62,126,64,130,66,134,68
%N A066043 a(1) = 1; for m > 0, a(2m) = 2m, a(2m+1) = 4m+2.
%C A066043 Length of period of sequences r(k,n) = floor(sinh(1)*k!) - n*floor(sinh(1)*k!/n) when n is fixed. - _Benoit Cloitre_, Jun 22 2003
%H A066043 Harry J. Smith, <a href="/A066043/b066043.txt">Table of n, a(n) for n = 1..1000</a>
%H A066043 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,2,0,-1).
%F A066043 O.g.f.: (x+2x^2+4x^3-x^5)/(1-x^2)^2. - _Len Smiley_, Dec 05 2001
%F A066043 a(n)*a(n+3) = -4 + a(n+1)*a(n+2).
%F A066043 From _Harry J. Smith_, Nov 08 2009: (Start)
%F A066043 a(n) = A109043(n), n > 1.
%F A066043 a(n) = 2*A026741(n), n > 1. (End)
%e A066043 r(k,7) is sequence 1, 2, 0, 0, 1, 6, 1, 1, 3, 2, 2, 3, 5, 0, 1, 2, 0, 0, 1, 6, 1, 1, 3, 2, 2, 3, 5, 0.... which is periodic with period (1, 2, 0, 0, 1, 6, 1, 1, 3, 2, 2, 3, 5, 0) of length 14 = a(7).
%t A066043 Join[{1}, LCM[Range[2, 100], 2]] (* _Paolo Xausa_, Feb 19 2024 *)
%o A066043 (PARI) a(n)=if(n<2,1,if(n%2,2*n,n))
%o A066043 (PARI) { for (n=1, 1000, a=if (n>1 && n%2, 2*n, n); write("b066043.txt", n, " ", a) ) } \\ _Harry J. Smith_, Nov 08 2009
%K A066043 easy,nonn
%O A066043 1,2
%A A066043 _George E. Antoniou_, Nov 30 2001