OFFSET
1,1
COMMENTS
All terms are even. - Alois P. Heinz, Aug 30 2020
Numbers of the form a^3 + b^3 where a divides b^3 and b divides a^3. - Robert Israel, Nov 01 2020
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
16 is in the sequence since 2 is a divisor of 16 and 2^3 + 2^3 = 16.
MAPLE
q:= n-> (s-> ormap(x-> n-x in s, s))(map(x-> x^3, numtheory[divisors](n))):
select(q, [2*i$i=1..17000])[]; # Alois P. Heinz, Aug 30 2020
N:= 50000: # to get terms <= N
R:= NULL:
for a from 1 to floor(N^(1/3)) do
Bs:= select(b -> b^3 + a^3 <= N and b^3 mod a = 0, numtheory:-divisors(a^3));
R:= R union map(b -> a^3 + b^3, Bs);
od:
sort(convert(R, list)); # Robert Israel, Nov 01 2020
MATHEMATICA
M = 40000; (* to get terms <= M *)
R = {};
For[a = 1, a <= Floor[M^(1/3)], a++,
Bs = Select[Divisors[a^3], #^3 + a^3 <= M && Mod[#^3, a] == 0&];
R = Union[R, a^3 + #^3& /@ Bs]];
Sort[R] (* Jean-François Alcover, Jan 01 2022, after Robert Israel *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Aug 30 2020
EXTENSIONS
a(12)-a(44) from Alois P. Heinz, Aug 30 2020
STATUS
approved