A077100 a(n) = lcm(A051612(n), A065387(n)), where A051612(n) = sigma(n) - phi(n) and A065387(n) = sigma(n) + phi(n).

0, 4, 6, 45, 10, 70, 14, 209, 133, 154, 22, 96, 26, 90, 32, 897, 34, 495, 38, 850, 220, 598, 46, 884, 561, 270, 638, 748, 58, 320, 62, 3713, 476, 1330, 72, 8137, 74, 546, 160, 3922, 82, 756, 86, 832, 918, 2350, 94, 3780, 495, 8249, 520, 4514, 106, 2346, 224

Offset: 1

Author

Labos Elemer, Nov 06 2002

Keywords

• nonn

Links

• Michael De Vlieger, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000010, A000203, A051612, A065387, A077099, A077101.

Programs

Mathematica

Table[LCM[#1 - #2, #1 + #2] & @@ {DivisorSigma[1, n], EulerPhi@ n}, {n, 55}] (* Michael De Vlieger, Dec 17 2016 *)

PARI

a(n)=my(f=factor(n),e=eulerphi(f),s=sigma(f)); lcm(s+e,s-e) \\ Charles R Greathouse IV, Nov 27 2013

Formula

If p is prime, then a(p) = 2*p.

Extensions

Edited by Dean Hickerson, Nov 07 2002