This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A077100 #19 Mar 25 2020 06:52:40
%S A077100 0,4,6,45,10,70,14,209,133,154,22,96,26,90,32,897,34,495,38,850,220,
%T A077100 598,46,884,561,270,638,748,58,320,62,3713,476,1330,72,8137,74,546,
%U A077100 160,3922,82,756,86,832,918,2350,94,3780,495,8249,520,4514,106,2346,224
%N A077100 a(n) = lcm(A051612(n), A065387(n)), where A051612(n) = sigma(n) - phi(n) and A065387(n) = sigma(n) + phi(n).
%H A077100 Michael De Vlieger, <a href="/A077100/b077100.txt">Table of n, a(n) for n = 1..10000</a>
%F A077100 If p is prime, then a(p) = 2*p.
%t A077100 Table[LCM[#1 - #2, #1 + #2] & @@ {DivisorSigma[1, n], EulerPhi@ n}, {n, 55}] (* _Michael De Vlieger_, Dec 17 2016 *)
%o A077100 (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
%Y A077100 Cf. A000010, A000203, A051612, A065387, A077099, A077101.
%K A077100 nonn
%O A077100 1,2
%A A077100 _Labos Elemer_, Nov 06 2002
%E A077100 Edited by _Dean Hickerson_, Nov 07 2002