OFFSET
1,2
FORMULA
a(n) = Sum_{k=1..n} Sum_{i=1..n} (1 - ceiling(n/(k^i)) + floor(n/(k^i))).
a(n) = A309891(n) + n. - Ridouane Oudra, Sep 28 2024
EXAMPLE
a(4) = 7; The 7 pairs are: (1,1), (1,2), (1,3), (1,4), (2,1), (2,2) and (4,1) since all of 1^1, 1^2, 1^3, 1^4, 2^1, 2^2 and 4^1 divide 4.
MAPLE
seq(add(padic[ordp](n, d), d in numtheory[divisors](n) minus {1}) + n, n=1..80); # Ridouane Oudra, Sep 28 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Feb 25 2022
STATUS
approved