OFFSET
1,3
COMMENTS
EXAMPLE
a(4)=7 because there are 9 unique products in the 4 X 4 multiplication table (1 2 3 4 6 8 9 12 16), which excludes 7 non-product integers within the range 1 to 16 (5 7 10 11 13 14 15).
PROG
(Python)
def A062851(n): return n**2-len({i*j for i in range(1, n+1) for j in range(1, i+1)}) # Chai Wah Wu, Oct 13 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
Ron A. Lalonde (ronronronlalonde(AT)hotmail.com), Jun 25 2001
STATUS
approved