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Numbers n such that ChebyshevT[16,n] is prime.
4

%I #11 Aug 13 2018 09:10:49

%S 2,13,20,21,33,74,87,88,94,104,105,127,172,182,185,188,215,224,233,

%T 240,249,258,278,281,292,293,304,329,337,365,399,416,433,440,468,471,

%U 489,502,509,529,540,573,576,583,608,612,615,622,630,631,639,685,689,707

%N Numbers n such that ChebyshevT[16,n] is prime.

%C ChebyshevT[16,x] is the 16th Chebyshev polynomial of the first kind evaluated at x.

%H Robert Israel, <a href="/A219278/b219278.txt">Table of n, a(n) for n = 1..10000</a>

%p P:= unapply(orthopoly[T](16,x),x):

%p select(isprime @ P, [$1..1000]); # _Robert Israel_, Aug 13 2018

%t lst={}; Do[If[PrimeQ[ChebyshevT [16, n]], AppendTo[lst, n]], {n, 10^3}]; lst

%t Select[Range[800],PrimeQ[ChebyshevT[16,#]]&] (* _Harvey P. Dale_, Jan 23 2016 *)

%o (PARI) is(n)=ispseudoprime(polchebyshev(16,1,n)) \\ _Charles R Greathouse IV_, May 22 2017

%Y Cf. A144131, A144132, A219276, A219277.

%K nonn

%O 1,1

%A _Michel Lagneau_, Nov 17 2012