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A275059 Numbers n such that A000010(n) + n^2 is a prime. 1

%I

%S 1,2,3,5,11,13,15,19,31,33,35,41,51,53,59,65,83,89,91,101,103,115,131,

%T 141,149,161,163,181,185,187,191,193,199,217,221,233,241,263,281,287,

%U 295,303,329,331,349,373,401,415,419,431,433,445,449,461,463,469,473,499,517

%N Numbers n such that A000010(n) + n^2 is a prime.

%C For n >= 2, a(n) is odd and squarefree. - _Robert Israel_, Jul 29 2016

%H Robert Israel, <a href="/A275059/b275059.txt">Table of n, a(n) for n = 1..10000</a>

%e 5 is a term because A000010(5) + 5^2 = 29 is a prime number.

%p select(t -> isprime(numtheory:-phi(t) + t^2), [1,2,seq(n,n=3..1000,2)]); # _Robert Israel_, Jul 29 2016

%t Select[Range[2000], PrimeQ[#^2 + EulerPhi[#]] &]

%o (MAGMA) [n: n in [1..800] | IsPrime(n^2+EulerPhi(n))];

%o (PARI) isok(n) = isprime(eulerphi(n) + n^2); \\ _Altug Alkan_, Jul 27 2016

%Y Cf. A000010, A259145.

%K nonn,easy

%O 1,2

%A _Vincenzo Librandi_, Jul 27 2016

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Last modified September 20 11:38 EDT 2021. Contains 347584 sequences. (Running on oeis4.)