A094181 a(n) = (n - tau(n))*(n - phi(n)), where tau=A000005 and phi=A000010.

0, 0, 1, 2, 3, 8, 5, 16, 18, 36, 9, 48, 11, 80, 77, 88, 15, 144, 17, 168, 153, 216, 21, 256, 110, 308, 207, 352, 27, 484, 29, 416, 377, 540, 341, 648, 35, 680, 525, 768, 39, 1020, 41, 912, 819, 1008, 45, 1216, 322, 1320, 893, 1288, 51, 1656, 765, 1536, 1113, 1620

Offset: 1

Author

Reinhard Zumkeller, May 06 2004

Keywords

• nonn

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A062355.

Programs

Magma

[(n-NumberOfDivisors(n))*(n-EulerPhi(n)): n in [1..60]]; // Vincenzo Librandi, Aug 31 2018

Mathematica

Array[(#-DivisorSigma[0,#])(#-EulerPhi[#])&,60] (* Harvey P. Dale, May 18 2012 *)

Formula

a(n) = A049820(n)*A051953(n).