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 A190815 A bisection of A049690. 3
 0, 3, 9, 17, 31, 45, 63, 87, 111, 139, 173, 205, 243, 287, 329, 373, 435, 487, 535, 607, 663, 727, 809, 877, 955, 1037, 1117, 1205, 1293, 1385, 1475, 1595, 1695, 1783, 1913, 2005, 2123, 2267, 2379, 2487, 2629, 2763, 2893, 3041, 3177, 3313, 3473, 3625, 3761 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Nathaniel Johnston, Table of n, a(n) for n = 1..10000 MAPLE 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 MATHEMATICA a[n_] := Sum[EulerPhi[2k], {k, 1, 2n-2}]; Table[a[n], {n, 1, 49}] (* Jean-François Alcover, Apr 16 2023 *) PROG (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 (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 CROSSREFS Cf. A000010, A049690, A099958. Sequence in context: A171152 A035107 A090262 * A006459 A349489 A049778 Adjacent sequences: A190812 A190813 A190814 * A190816 A190817 A190818 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, May 20 2011 EXTENSIONS More terms from Nathaniel Johnston, May 24 2011 STATUS approved

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Last modified July 13 09:39 EDT 2024. Contains 374274 sequences. (Running on oeis4.)