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 A190815 #18 Dec 03 2023 18:35:21
%S A190815 0,3,9,17,31,45,63,87,111,139,173,205,243,287,329,373,435,487,535,607,
%T A190815 663,727,809,877,955,1037,1117,1205,1293,1385,1475,1595,1695,1783,
%U A190815 1913,2005,2123,2267,2379,2487,2629,2763,2893,3041,3177,3313,3473,3625,3761
%N A190815 A bisection of A049690.
%H A190815 Nathaniel Johnston, <a href="/A190815/b190815.txt">Table of n, a(n) for n = 1..10000</a>
%p A190815 A190815 := proc(n) option remember: if(n=1)then return 0:fi: return procname(n-1)+numtheory[phi](4*n-6)+numtheory[phi](4*n-4): end: seq(A190815(n),n=1..49); # _Nathaniel Johnston_, May 24 2011
%t A190815 a[n_] := Sum[EulerPhi[2k], {k, 1, 2n-2}];
%t A190815 Table[a[n], {n, 1, 49}] (* _Jean-François Alcover_, Apr 16 2023 *)
%o A190815 (Magma) [n eq 1 select 0 else (&+[EulerPhi(2*j): j in [1..2*(n-1)]]) : n in [1..60] ]; // _G. C. Greubel_, Dec 03 2023
%o A190815 (SageMath) [sum(euler_phi(2*j) for j in range(1,2*n-1)) for n in range(1,61)] # _G. C. Greubel_, Dec 03 2023
%Y A190815 Cf. A000010, A049690, A099958.
%K A190815 nonn,easy
%O A190815 1,2
%A A190815 _N. J. A. Sloane_, May 20 2011
%E A190815 More terms from _Nathaniel Johnston_, May 24 2011