OFFSET
1,2
COMMENTS
May be called lesser of twin Löschian pairs.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
3 is a term because 3 = 1^2 + 1*1 + 1^2 and 3 + 1 = 4 = 0^2 + 0*2 + 2^2.
MATHEMATICA
Select[Range[0, 1400], AllTrue[{#, # + 1}, Resolve[Exists[{x, y}, Reduce[# == x^2 + x y + y^2, {x, y}, Integers]]] &] &] (* Version 10, or *)
Select[Range[0, 1400], Times @@ Boole@ Map[Resolve[Exists[{x, y}, Reduce[# == x^2 + x y + y^2, {x, y}, Integers]]] &, {#, # + 1}] == 1 &] (* Michael De Vlieger, Apr 01 2016 *)
PROG
(PARI) has(n) = #bnfisintnorm(bnfinit(z^2+z+1), n);
print1(0, ", "); for(n=1, 2000, if(has(n) && has(n+1), print1(n, ", ")));
CROSSREFS
KEYWORD
nonn
AUTHOR
Altug Alkan, Apr 01 2016
STATUS
approved