A077100 - OEIS

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

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

FORMULA

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

MATHEMATICA

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

PROG

(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

CROSSREFS