A228062 Numbers not expressible as a*b + b*c + a*c + 1 with positive numbers a, b, c.

1, 2, 3, 5, 7, 11, 19, 23, 31, 43, 59, 71, 79, 103, 131, 191, 211, 331, 463

Offset: 1

Author

T. D. Noe, Sep 13 2013

Keywords

• nonn
• fini

Comments

Except for the first term, all terms are prime. There is at most one more term.

Crossrefs

Cf. A025052.

Programs

Mathematica

nn = 250; t = Select[Union[Flatten[Table[a*b + b*c + a*c + 1, {a, nn}, {b, a, nn}, {c, b, nn}]]], # <= 2*nn + 1 &]; Complement[Range[2*nn + 1], t]