A190815 A bisection of A049690.

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

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