A216538 Numbers n such that the n-th Lucas number is prime, but cannot be written in the form a^2 + 7*b^2.

2, 8, 11, 13, 31, 41, 47, 61, 79, 313, 617, 863, 1097, 4793, 5851, 7741, 12251, 13963, 35449, 36779, 44507, 89849, 140057, 148091, 202667, 387433, 443609, 574219, 631181, 651821

Offset: 1

Author

V. Raman, Sep 08 2012

Keywords

• nonn

Links

• Blair Kelly, Factorizations of Fibonacci and Lucas numbers

Crossrefs

Cf. A000032, A001606.