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 A296213 a(n) = 1 if both 1+phi(k) and 1+sigma(k) are squares, 0 otherwise. 2
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 OFFSET 1 COMMENTS Characteristic function of A063532, numbers k such that phi(k) + 1 = x^2 and sigma(k) + 1 = y^2 for some x and y. LINKS Antti Karttunen, Table of n, a(n) for n = 1..65593 EXAMPLE a(15) = 1 because both 1+phi(15) = 9 and 1+sigma(15) = 25 are squares. MATHEMATICA Table[If[AllTrue[{Sqrt[1+EulerPhi[n]], Sqrt[1+DivisorSigma[1, n]]}, IntegerQ], 1, 0], {n, 130}] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Dec 22 2018 *) PROG (Scheme) (define (A296213 n) (* (A010052 (+ 1 (A000010 n))) (A010052 (+ 1 (A000203 n))))) (define (A296213 n) (if (zero? (A010052 (+ 1 (A000010 n)))) 0 (A010052 (+ 1 (A000203 n))))) CROSSREFS Sequence in context: A101637 A011729 A297044 * A277161 A216038 A011728 Adjacent sequences:  A296210 A296211 A296212 * A296214 A296215 A296216 KEYWORD nonn AUTHOR Antti Karttunen, Dec 08 2017 STATUS approved

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Last modified August 20 03:48 EDT 2019. Contains 326139 sequences. (Running on oeis4.)