OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
MAPLE
filter:= proc(n)
not issqr(n) and
ormap(k -> issqr(-3*k^4+3*k^2+36*k*n) and ((3*k-3*k^2+sqrt(-3*k^4+3*k^2+36*k*n))/(6*k))::integer,
numtheory:-divisors(6*n))
end proc:
select(filter, [$1..1000]); # Robert Israel, Jan 22 2017
MATHEMATICA
filterQ[n_] := !IntegerQ[Sqrt[n]] && AnyTrue[Divisors[6n], IntegerQ[Sqrt[-3 #^4 + 3 #^2 + 36 # n]] && IntegerQ[(3 # - 3 #^2 + Sqrt[-3 #^4 + 3 #^2 + 36 # n])/(6#)]&];
Select[Range[1000], filterQ] (* Jean-François Alcover, Jun 08 2020, after Maple *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Max Alekseyev, Apr 26 2012
STATUS
approved