A272903 Least nonnegative integer x such that n^2+nx-2n-x is prime.

2, 0, 1, 1, 1, 1, 5, 1, 1, 1, 1, 2, 1, 2, 1, 1, 5, 2, 1, 1, 1, 4, 5, 1, 17, 1, 3, 1, 13, 1, 1, 2, 3, 2, 1, 2, 5, 1, 1, 4, 1, 2, 5, 1, 1, 1, 13, 1, 11, 1, 3, 5, 1, 1, 1, 1, 5, 7, 1, 1, 11, 2, 3, 1, 1, 1, 7, 1, 3, 1, 11, 3, 5, 2, 3, 1, 17, 3, 7, 4, 3, 7, 1, 3, 1, 1, 3, 2, 1, 3, 11, 2, 1, 1, 7, 1, 17, 5, 9

Offset: 2

Author

Cody M. Haderlie, May 09 2016

Keywords

• nonn

Comments

The offset is 2 because n^2+nx-2n-x = -1 for n = 1 and all x.

a(n) seems to be exclusively prime or a product of two previous terms, and less than n excluding n = 2. x is most frequently equal to 1.

Links

• Cody M. Haderlie, Table of n, a(n) for n = 2..10000

Programs

Mathematica

Table[Min[DeleteCases[Table[If[PrimeQ[n^2+n*x-2n-x],x],{x,0,n}],Null]],{n,2,100}] (*Assuming that xHarvey P. Dale, May 12 2019 *)