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%I #21 Jun 09 2020 03:07:25
%S 17,73,89,193,337,521,953,1009,1249,1657,2377,2833,3329,3433,4441,
%T 4561,5849,6553,7297,8081,8737,9769,11617,12401,12601,13417,15569,
%U 16937,17881,18121,20353,21649,27529,28729,29033,30577,33457,35449,36809,46273,49801
%N Primes of the form (k^2+4)/5.
%C Also equal to primes p such that 5*p-4 is a perfect square.
%H Chai Wah Wu, <a href="/A245042/b245042.txt">Table of n, a(n) for n = 1..1000</a>
%t Select[(Range[500]^2+4)/5,PrimeQ] (* _Harvey P. Dale_, Jul 13 2014 *)
%o (Python)
%o import sympy
%o L = (k**2 + 4 for k in range(10**3))
%o [n//5 for n in L if n % 5 == 0 and sympy.ntheory.isprime(n//5)]
%Y Cf. A154418.
%Y Cf. A154616, A002327, A066436.
%K nonn
%O 1,1
%A _Chai Wah Wu_, Jul 10 2014
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