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 A066785 #14 Dec 19 2024 21:16:01
%S A066785 603,1414,1444,2093,7434,12822,66584,66960,91000,138645,160130,167400,
%T A066785 169212,210476,218592,229026,236572,265977,304128,344790,493722,
%U A066785 618570,754110,950158,1091385,1113480,1760616,1761409,2116116,2733131,2776928
%N A066785 Numbers k such that (k, phi(k), sigma(k)) lies on a sphere with integral radius centered at the origin, i.e., k^2 + phi(k)^2 + sigma(k)^2 is a square.
%H A066785 Harry J. Smith, <a href="/A066785/b066785.txt">Table of n, a(n) for n = 1..82</a>
%e A066785 603^2 + phi(603)^2 + sigma(603)^2 = 603^2 + 396^2 + 884^2 = 1141^2, so 603 is a term of the sequence.
%t A066785 Select[ Range[ 1, 10^6 ], IntegerQ[ Sqrt[ #^2 + DivisorSigma[ 1, # ]^2 + EulerPhi[ # ]^2 ] ] & ]
%o A066785 (PARI) isok(k) = { issquare(k^2 + eulerphi(k)^2 + sigma(k)^2) } \\ _Harry J. Smith_, Mar 25 2010
%Y A066785 Cf. A066763, A066764.
%K A066785 nonn
%O A066785 1,1
%A A066785 _Joseph L. Pe_, Jan 18 2002
%E A066785 Terms a(25)-a(31) from _Harry J. Smith_, Mar 25 2010