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

1,2

Comments

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

Links

Table of n, a(n) for n=1..19.

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]

Crossrefs

Cf. A025052.

Sequence in context: A278694 A214837 A079346 * A332216 A059878 A105017

Adjacent sequences: A228059 A228060 A228061 * A228063 A228064 A228065

Keyword

nonn,fini

Author

T. D. Noe, Sep 13 2013

Status

approved