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 A084184 #24 Jan 29 2017 01:59:48
%S A084184 0,1,2,7,10,31,42,127,170,511,682,2047,2730,8191,10922,32767,43690,
%T A084184 131071,174762,524287,699050,2097151,2796202,8388607,11184810,
%U A084184 33554431,44739242,134217727,178956970,536870911,715827882,2147483647,2863311530,8589934591
%N A084184 Partial sums of a Jacobsthal related sequence.
%C A084184 Partial sums of A084183.
%H A084184 Colin Barker, <a href="/A084184/b084184.txt">Table of n, a(n) for n = 0..1000</a>
%H A084184 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,5,0,-4).
%F A084184 G.f.: x*(1+2*x+2*x^2) / ((1-x^2)*(1-4*x^2)). - typo fixed by _Colin Barker_, Sep 09 2016
%F A084184 a(2*n+1) = A083420(n). a(2*n) = 2*A002450(n) = 2*A001045(2*n).
%F A084184 From _Colin Barker_, Sep 09 2016: (Start)
%F A084184 a(n) = (5-(-1)^n)*(2^n-1)/6.
%F A084184 a(n) = 5*a(n-2) - 4*a(n-4) for n>3.
%F A084184 (End)
%p A084184 A084184:=n->(5-(-1)^n)*(2^n-1)/6: seq(A084184(n), n=0..50); # _Wesley Ivan Hurt_, Jan 28 2017
%t A084184 LinearRecurrence[{0,5,0,-4},{0,1,2,7},40] (* _Harvey P. Dale_, Jan 18 2015 *)
%o A084184 (PARI) concat(0, Vec(x*(1+2*x+2*x^2)/((1-x^2)*(1-4*x^2)) + O(x^40))) \\ _Colin Barker_, Sep 09 2016
%Y A084184 Cf. A001045, A002450, A083420, A084183.
%K A084184 easy,nonn
%O A084184 0,3
%A A084184 _Paul Barry_, May 19 2003