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A200652 a(n) = least k with -3<k<2*n such that n*(n+1)+k and n*(n+1)+k+2 are twin primes, or 0 if no such k exists. 2
1, -1, -1, 0, -1, -1, 3, -1, 11, 0, 5, 23, 9, 17, -1, 9, 5, 5, 0, -1, -1, 15, 17, -1, 9, 0, 53, 9, 11, 0, 27, 5, 29, 39, 17, 0, 21, -1, 47, 27, -1, 65, 39, 17, 11, 75, 11, 29, 0, -1, 5, 33, 0, -1, 39, 59, 23, 39, -1, 11, 39, 11, 17, 57, 47, -1, 81, 29, 101, 39, 119, 23, 15, 89, 41 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,7

COMMENTS

Only 11 values are zero for n < 434. Conjecture: no more 0 values if n>433.

LINKS

Pierre CAMI, Table of n, a(n) for n = 1..10000

MAPLE

A200652 := proc(n)

    for k from -2 to 2*n-1 do

        if isprime(n*(n+1)+k) and isprime(n*(n+1)+k+2) then

            return k;

        end if;

    end do:

    return 0 ;

end proc:

seq(A200652(n), n=1..80) ; # R. J. Mathar, Nov 22 2011

CROSSREFS

Cf. A200653.

Sequence in context: A225753 A210725 A048953 * A276391 A119632 A201131

Adjacent sequences:  A200649 A200650 A200651 * A200653 A200654 A200655

KEYWORD

sign

AUTHOR

Pierre CAMI, Nov 20 2011

STATUS

approved

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Last modified November 18 18:33 EST 2018. Contains 317324 sequences. (Running on oeis4.)