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A121834 Primes p of the form 4*n^2 + 1 such that 4*p^2+1 is also prime. 2
5, 37, 677, 1297, 2917, 8837, 13457, 50177, 147457, 156817, 246017, 341057, 414737, 746497, 1136357, 1726597, 1833317, 2119937, 2802277, 2808977, 3013697, 3549457, 3865157, 3896677, 4104677, 4384837, 5354597, 5410277, 5779217, 6031937, 6635777, 7001317 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Intersection of A001912 and A121326. Except for the first term all other terms are == 7 (mod 10). Also all the primes 4*p^2+1 are == 7 (mod 10). - Zak Seidov, Mar 05 2015

LINKS

Table of n, a(n) for n=1..32.

MATHEMATICA

fpQ[n_]:=PrimeQ[n]&&PrimeQ[4n^2+1]; Select[4Range[2000]^2+1, fpQ] (* Harvey P. Dale, Nov 07 2016 *)

PROG

(PARI) isA121834(n)={ if( (n-1) %4, return(0) ; ) ; if( issquare((n-1)/4), if( isprime(4*n^2+1), return(1), return(0) ), return(0) ; ) ; } { for(i=1, 1000000, p=prime(i) ; if( isA121834(p), print1(p, ", ") ; ) ; ) ; } /* R. J. Mathar, Sep 01 2006*/

CROSSREFS

Cf. A002496, A052291, A121326.

Sequence in context: A244820 A246534 A095957 * A215233 A083846 A180275

Adjacent sequences:  A121831 A121832 A121833 * A121835 A121836 A121837

KEYWORD

nonn

AUTHOR

Zak Seidov, Aug 28 2006

EXTENSIONS

More terms from R. J. Mathar, Sep 01 2006

STATUS

approved

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Last modified February 21 01:12 EST 2019. Contains 320364 sequences. (Running on oeis4.)