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 A328984 #26 May 23 2021 02:56:59
%S A328984 1,3,7,5,11,8,17,10,21,13,27,15,31,18,37,20,41,23,47,25,51,28,57,30,
%T A328984 61,33,67,35,71,38,77,40,81,43,87,45,91,48,97,50,101,53,107,55,111,58,
%U A328984 117,60,121,63,127,65,131,68,137,70,141,73,147,75,151,78
%N A328984 If n is even, a(n) = floor((5t+1)/2) where t=n/2; if n == 1 (mod 4) then a(n) = 10t+1 where t = (n-1)/4; and if n == 3 (mod 4) then a(n) = 10t+7 where t = (n-3)/4.
%C A328984 This is a simplified version of A328190. It does not quite have the defining property of that sequence, which is that the sequence and its first differences together are disjoint. For the present sequence the first differences are in A328985, and the intersection of the sequence and its first differences are the numbers >= 11 that are congruent to 1 (mod 10).
%C A328984 The graphs of A328190 and this sequence are essentially identical.
%H A328984 N. J. A. Sloane, <a href="/A328984/b328984.txt">Table of n, a(n) for n = 1..10000</a>
%H A328984 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (0,1,0,1,0,-1).
%F A328984 From _Colin Barker_, Nov 07 2019: (Start)
%F A328984 G.f.: x*(1 + 3*x + 6*x^2 + 2*x^3 + 3*x^4) / ((1 - x^2)*(1 - x^4)).
%F A328984 a(n) = a(n-2) + a(n-4) - a(n-6) for n > 6.
%F A328984 (End)
%t A328984 Table[Which[EvenQ[n],Floor[(5 n/2+1)/2],Mod[n,4]==1,10 (n-1)/4+1,True,10 (n-3)/4+7],{n,70}]
%Y A328984 Cf. A328190, A328196, A328985.
%K A328984 nonn,easy
%O A328984 1,2
%A A328984 _N. J. A. Sloane_, Nov 06 2019