A086700 Euler phi function applied to the triangular numbers.

1, 2, 2, 4, 8, 12, 12, 12, 24, 40, 20, 24, 72, 48, 32, 64, 96, 108, 72, 48, 120, 220, 88, 80, 240, 216, 108, 168, 224, 240, 240, 160, 320, 384, 144, 216, 648, 432, 192, 320, 480, 504, 420, 240, 528, 1012, 368, 336, 840, 640, 384, 624, 936, 720, 480, 432, 1008, 1624, 464, 480, 1800, 1080, 576, 768, 960, 1320

Offset

1,2

Links

Michel Marcus, Table of n, a(n) for n = 1..5000

Formula

a(n) = A000010(A000217(n)). - Michel Marcus, Aug 21 2017

Example

a(3) = phi(6) = 2.

Maple

with(numtheory):with(combinat):a:=n->phi(binomial(n, 2)): seq(a(n), n=2..31); # Zerinvary Lajos, Oct 05 2007

Mathematica

EulerPhi[Accumulate[Range[70]]] (* Harvey P. Dale, Sep 16 2012 *)

Prog

(PARI) vector(66, n, eulerphi(n*(n+1)/2))
(Sage) [euler_phi(binomial(n, 2)) for n in range(2, 32)] # Zerinvary Lajos, Jun 06 2009

Crossrefs

Cf. A000010, A000217.

Sequence in context: A019463 A152763 A221666 * A332004 A364669 A104221

Adjacent sequences: A086697 A086698 A086699 * A086701 A086702 A086703

Keyword

nonn

Author

Jon Perry, Jul 28 2003

Status

approved