OFFSET
1,1
COMMENTS
Numbers that can be represented in at least one way as 3*a*(a^2 + 2*b^2) for positive integers a and b.
In contrast to A306213, the arithmetic progression need not consist only of positive numbers.
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
a(4) = 57 is a term because 57 = (-2)^3 + 1^3 + 4^3 where (-2, 1, 3) are in arithmetic progression.
MAPLE
N:= 2000: # for terms <= N
L:= NULL:
for a from 1 while 3*a^3 <= N do
for b from 1 do
x:= 3*a*(a^2 + 2*b^2);
if x > N then break fi;
L:= L, x
od od:
sort(convert({L}, list));
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert Israel, Dec 15 2022
STATUS
approved