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A245042 Primes of the form (k^2+4)/5. 2
17, 73, 89, 193, 337, 521, 953, 1009, 1249, 1657, 2377, 2833, 3329, 3433, 4441, 4561, 5849, 6553, 7297, 8081, 8737, 9769, 11617, 12401, 12601, 13417, 15569, 16937, 17881, 18121, 20353, 21649, 27529, 28729, 29033, 30577, 33457, 35449, 36809, 46273, 49801 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Also equal to primes p such that 5*p-4 is a perfect square.

LINKS

Chai Wah Wu, Table of n, a(n) for n = 1..1000

MATHEMATICA

Select[(Range[500]^2+4)/5, PrimeQ] (* Harvey P. Dale, Jul 13 2014 *)

PROG

(Python)

import sympy

L = (k**2 + 4 for k in range(10**3))

[n//5 for n in L if n % 5 == 0 and sympy.ntheory.isprime(n//5)]

CROSSREFS

Cf. A154418.

Cf. A154616, A002327, A066436.

Sequence in context: A337704 A121243 A039371 * A144245 A307718 A139919

Adjacent sequences:  A245039 A245040 A245041 * A245043 A245044 A245045

KEYWORD

nonn

AUTHOR

Chai Wah Wu, Jul 10 2014

STATUS

approved

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Last modified January 26 20:02 EST 2022. Contains 350599 sequences. (Running on oeis4.)