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A175282 Positive numbers n with property that n^2+3n+9 is prime (A005471). 4
1, 2, 4, 7, 8, 10, 11, 16, 17, 23, 25, 28, 29, 31, 32, 37, 38, 43, 49, 50, 56, 58, 64, 70, 73, 85, 88, 91, 94, 95, 98, 101, 107, 112, 121, 122, 127, 130, 133, 134, 136, 140, 142, 143, 155, 158, 163, 164, 169, 172, 175, 176, 179, 182, 197, 200, 205, 206, 212, 214, 218 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Notice that at n=-1, n^2+3n+9=7 is also (positive) prime.

LINKS

Table of n, a(n) for n=1..61.

Erik Dofs, Solutions of x^3+y^3+z^3=n*x*y*z, Acta Arithm. 73.3 (1995) 201

MAPLE

A175282 := proc(n)

    option remember;

    if n = 1 then

        1;

    else

        for a from procname(n-1)+1 do

            if isprime(a^2+3*a+9) then

                return a;

            end if;

        end do;

    end if;

end proc: # R. J. Mathar, Jun 06 2019

MATHEMATICA

Select[Range[1, 400], PrimeQ[ #^2+3*#+9]&]

CROSSREFS

Cf. A005471, A175281.

Sequence in context: A075663 A325419 A139212 * A127875 A056231 A248637

Adjacent sequences:  A175279 A175280 A175281 * A175283 A175284 A175285

KEYWORD

nonn

AUTHOR

Zak Seidov, Mar 21 2010

STATUS

approved

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Last modified July 12 19:26 EDT 2020. Contains 335668 sequences. (Running on oeis4.)