OFFSET
1,1
COMMENTS
All numbers in this sequence are divisible by primes A139513
REFERENCES
Dirichlet & Dedekins Lectures on Number Theory (English Translation 1999) p. 119.
MATHEMATICA
a = {}; Do[Do[k = x^2 + 5 y^2; If[OddQ[k], If[Mod[k, 5] != 0, AppendTo[a, k]]], {x, 1, 100}], {y, 1, 100}]; Union[a] (*Artur Jasinski*)
With[{upto=1000}, Select[Union[#[[1]]^2+5#[[2]]^2&/@Tuples[Range[Floor[ Sqrt[ upto-5]]], 2]], OddQ[#]&&Mod[#, 5]!=0&&#<=upto&]] (* Harvey P. Dale, Jul 25 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Artur Jasinski, Apr 25 2008, Apr 28 2008
EXTENSIONS
Definition clarified by Harvey P. Dale, Jul 25 2019
STATUS
approved