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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
OFFSET
1,1
LINKS
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
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Apr 27 2003
STATUS
approved