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A082466 Least k>=1 such that n^2+kn-1 and n^2+kn+1 are twin primes. 3
3, 1, 1, 11, 1, 1, 53, 1, 3, 5, 7, 3, 11, 16, 1, 11, 43, 6, 11, 1, 1, 8, 13, 1, 17, 7, 3, 11, 43, 4, 11, 4, 7, 8, 31, 9, 17, 1, 9, 35, 1, 4, 53, 4, 7, 41, 43, 6, 23, 1, 17, 8, 67, 1, 5, 4, 17, 11, 1, 7, 197, 4, 3, 11, 25, 1, 227, 7, 3, 14, 157, 19, 11, 16, 3, 71, 43, 6, 53, 7, 7, 44, 31, 3, 41 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

R. J. Mathar, Table of n, a(n) for n = 1..1000

MAPLE

A082466 := proc(n)

    local k, p ;

    for k from 1 do

        p := (n+k)*n-1 ;

        if isprime(p) and isprime(p+2) then

            return k;

        end if;

    end do:

end proc: # R. J. Mathar, Jul 20 2012

MATHEMATICA

lk[n_]:=Module[{k=1}, While[!And@@PrimeQ[n^2+k*n+{1, -1}], k++]; k]; Array[ lk, 90] (* Harvey P. Dale, Nov 25 2013 *)

PROG

(PARI) a(n)=if(n<0, 0, k=1; while(isprime(n^2+k*n+1)*isprime(n^2+k*n-1)==0, s++); k)

CROSSREFS

Sequence in context: A100265 A086766 A078688 * A120270 A243752 A113711

Adjacent sequences:  A082463 A082464 A082465 * A082467 A082468 A082469

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Apr 27 2003

STATUS

approved

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Last modified October 19 16:17 EDT 2019. Contains 328223 sequences. (Running on oeis4.)