login
A085710
Smallest k such that kn+1 is a semiprime.
2
3, 4, 1, 2, 1, 4, 2, 1, 1, 2, 3, 2, 1, 1, 3, 2, 2, 3, 2, 1, 1, 5, 4, 1, 1, 7, 2, 2, 5, 3, 3, 1, 1, 1, 3, 4, 1, 1, 3, 3, 5, 2, 2, 3, 1, 2, 2, 1, 6, 1, 4, 4, 4, 1, 2, 1, 1, 5, 2, 2, 1, 3, 4, 1, 5, 2, 3, 1, 5, 2, 2, 2, 1, 5, 3, 1, 2, 3, 2, 2, 1, 3, 10, 1, 1, 1, 3, 2, 5, 1, 2, 1, 1, 1, 4, 3, 6, 3, 3, 2, 2, 2, 4, 2, 1
OFFSET
1,1
COMMENTS
Conjecture: for every n > 2 there exists a number k < n such that n*k + 1 is a semiprime.
MATHEMATICA
sk[n_]:=Module[{k=1}, While[PrimeOmega[k*n+1]!=2, k++]; k]; Array[sk, 120] (* Harvey P. Dale, Mar 12 2019 *)
CROSSREFS
Cf. A001358.
Sequence in context: A204999 A373828 A294731 * A248004 A106650 A076942
KEYWORD
easy,nonn
AUTHOR
Jason Earls, Jul 19 2003
STATUS
approved