OFFSET
0,2
COMMENTS
a(9) > 5*10^9. - Jon E. Schoenfield, Jan 13 2022
EXAMPLE
a(3) = 57603 as 57603 has the three representations 57603 = 2^2 + 2*239 + 239^2 = 31^2 + 31*223 + 223^2 = 101^2 + 101*173 + 173^2 and no smaller number has this property.
MAPLE
N:= 10^9:
Q:= Vector(N, datatype=integer[4]):
P:= select(isprime, [2, seq(i, i=3..floor(sqrt(N)), 2)]):
T:= Array(0..7): T[0]:= 1:
nP:= nops(P):
for i from 1 to nP do
for j from 1 to i do
v:= P[i]^2 + P[i]*P[j] + P[j]^2;
if v > N then break fi;
Q[v]:= Q[v]+1;
if T[Q[v]] = 0 or v < T[Q[v]] then T[Q[v]]:= v fi
od od:
convert(T, list);
CROSSREFS
KEYWORD
nonn,more
AUTHOR
J. M. Bergot and Robert Israel, Jan 09 2022
EXTENSIONS
a(8) from Jon E. Schoenfield, Jan 13 2022
a(9)-a(20) from Martin Ehrenstein, Jan 24 2022
STATUS
approved