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A075577 n^2 is a member if n^2 +(n-1)^2 and n^2 +(n+1)^2 are primes. 1
4, 25, 625, 900, 1225, 4900, 7225, 10000, 12100, 50625, 52900, 67600, 81225, 84100, 102400, 152100, 168100, 225625, 240100, 245025, 265225, 348100, 462400, 483025, 504100, 562500, 577600, 714025, 902500, 1166400, 1210000, 1288225, 1380625 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

a(2) onwards a(n)== 0 (mod 25).

LINKS

Table of n, a(n) for n=0..32.

EXAMPLE

900 is here because {m=30,b=m^2,a=(m-1)^2,c=(m+1)^2,q1=a+b,q2=b+c,PrimeQ[q1],PrimeQ[q2]}= {30, 900, 841, 961, 1741, 1861, True, True}

MATHEMATICA

Do[s=n^2+(n-1)^2; s1=n^2+(n+1)^2; If[PrimeQ[s]&&PrimeQ[s1], Print[n^2]], {n, 1, 5000}]

CROSSREFS

Sequence in context: A086216 A167041 A123129 * A004019 A302092 A277110

Adjacent sequences:  A075574 A075575 A075576 * A075578 A075579 A075580

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Sep 25 2002

EXTENSIONS

More terms from Labos Elemer, Sep 27 2002

STATUS

approved

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Last modified September 29 10:06 EDT 2020. Contains 337428 sequences. (Running on oeis4.)