A064485 Number of ordered pairs a,b of elements in the dihedral group D_2n such that the subgroup generated by the pair a,b is a proper subgroup of D_2n.

1, 10, 18, 40, 40, 108, 70, 160, 162, 280, 154, 432, 208, 532, 540, 640, 340, 972, 418, 1120, 1008, 1276, 598, 1728, 1000, 1768, 1458, 2128, 928, 2880, 1054, 2560, 2376, 2992, 2380, 3888, 1480, 3724, 3276, 4480, 1804, 5544, 1978, 5104, 4860, 5428, 2350, 6912

Offset

1,2

Links

Table of n, a(n) for n=1..48.

Formula

a(n) = 4*n^2 - A064400(n) = 4*n^2 - 3*n*phi(n).

Maple

with(numtheory): A064485:=n->4*n^2-3*n*phi(n): seq(A064485(n), n=1..50); # Wesley Ivan Hurt, Oct 08 2014

Mathematica

Table[4 n^2 - 3 n*EulerPhi[n], {n, 50}] (* Wesley Ivan Hurt, Oct 08 2014 *)

Crossrefs

Cf. A064400, A064279.

Sequence in context: A363769 A153360 A189323 * A007938 A007937 A300601

Adjacent sequences: A064482 A064483 A064484 * A064486 A064487 A064488

Keyword

nonn

Author

Dan Fux (dan.fux(AT)OpenGaia.com or danfux(AT)OpenGaia.com), Oct 03 2001

Extensions

More terms from Eric M. Schmidt, Oct 08 2014

Status

approved