OFFSET
0,2
LINKS
David A. Corneth, Table of n, a(n) for n = 0..3000 (first 999 terms from R. H. Hardin)
David A. Corneth, PARI program
EXAMPLE
a(3) = 16 as the possible products i*j where 0 <= i, j <= 3 are 0, 1, 2, 3, 4, 6, 9. From these numbers we can find the 16 distinct sums, listed with a few examples, 0, 1, 2, 3, 4, 5, 6, 7 = 3+4, 8, 9, 10, 11, 12 = 6+6, 13 = 4+9, 15, 18. - David A. Corneth, Sep 07 2023
PROG
(PARI) a(n) = #setbinop((x, y)->x+y, setbinop((x, y)->x*y, [0..n])); \\ Michel Marcus, Sep 06 2023
(PARI) See PARI link \\ David A. Corneth, Sep 07 2023
(Python)
from itertools import combinations_with_replacement
def A225253(n): return len({x+y for x, y in combinations_with_replacement({i*j for i in range(n+1) for j in range(i+1)}, 2)}) # Chai Wah Wu, Oct 13 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, May 04 2013
EXTENSIONS
a(0)=1 prepended by Alois P. Heinz, Oct 13 2023
STATUS
approved