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 A238463 Numbers n such that phi(n) * sigma(n) + 1 is a perfect square. 1
 2, 3, 5, 6, 7, 11, 13, 17, 19, 22, 23, 29, 31, 33, 37, 41, 43, 44, 47, 53, 59, 61, 67, 69, 71, 73, 76, 79, 82, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 140, 149, 151, 157, 163, 167, 173, 179, 181, 190, 191, 193, 197, 199, 211, 223, 227, 229 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 MATHEMATICA Select[Range[1000], IntegerQ[Sqrt[EulerPhi[#]DivisorSigma[1, #] + 1]]&] PROG (MAGMA) [n: n in [1..300] | IsSquare(EulerPhi(n) * SumOfDivisors(n) + 1)] CROSSREFS Cf. A015727, A015728, A015729. Sequence in context: A299157 A325327 A003174 * A166070 A053813 A116974 Adjacent sequences:  A238460 A238461 A238462 * A238464 A238465 A238466 KEYWORD nonn AUTHOR Vincenzo Librandi, Mar 14 2014 STATUS approved

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Last modified December 7 18:12 EST 2019. Contains 329847 sequences. (Running on oeis4.)