A100447 Bisection of A000031.

2, 4, 8, 20, 60, 188, 632, 2192, 7712, 27596, 99880, 364724, 1342184, 4971068, 18512792, 69273668, 260301176, 981706832, 3714566312, 14096303344, 53634713552, 204560302844, 781874936816, 2994414645860, 11488774559636

Offset: 0

Author

N. J. A. Sloane, Nov 21 2004

Keywords

• nonn
• easy

Crossrefs

Cf. A000031, A100446. Equals 2*A026119.

Programs

Maple

with(numtheory):seq((1/(2*n+1))*add(phi(d)*2^((2*n+1)/d),d=divisors(2*n+1)),n=0..30); (C. Ronaldo)

Extensions

More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 19 2005