A082466 Least k>=1 such that n^2+kn-1 and n^2+kn+1 are twin primes.

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

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