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A066785 Numbers n such that (n, phi(n), sigma(n)) lies on a sphere with integral radius centered at the origin, i.e., n^2 + phi(n)^2 + sigma(n)^2 is a square. 1
603, 1414, 1444, 2093, 7434, 12822, 66584, 66960, 91000, 138645, 160130, 167400, 169212, 210476, 218592, 229026, 236572, 265977, 304128, 344790, 493722, 618570, 754110, 950158, 1091385, 1113480, 1760616, 1761409, 2116116, 2733131, 2776928 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
603^2 + phi(603)^2 + sigma(603)^2 = 603^2 + 396^2 + 884^2 = 1141^2, so 603 is a term of the sequence.
MATHEMATICA
Select[ Range[ 1, 10^6 ], IntegerQ[ Sqrt[ #^2 + DivisorSigma[ 1, # ]^2 + EulerPhi[ # ]^2 ] ] & ]
PROG
(PARI) { n=0; for (m=1, 10^10, if (issquare(m^2 + eulerphi(m)^2 + sigma(m)^2), write("b066785.txt", n++, " ", m); if (n==100, return)) ) } \\ Harry J. Smith, Mar 25 2010
CROSSREFS
Sequence in context: A145331 A252957 A348077 * A178032 A107256 A177685
KEYWORD
nonn
AUTHOR
Joseph L. Pe, Jan 18 2002
EXTENSIONS
Terms a(25) - a(31) from Harry J. Smith, Mar 25 2010
STATUS
approved

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Last modified March 29 06:44 EDT 2024. Contains 371265 sequences. (Running on oeis4.)