login
Number of ordered pairs, (s,t), 1 <= s <= t, such that (t^s) | n.
0

%I #8 Feb 14 2022 22:19:57

%S 1,2,2,4,2,4,2,5,4,4,2,7,2,4,4,7,2,7,2,7,4,4,2,9,4,4,6,7,2,8,2,8,4,4,

%T 4,12,2,4,4,9,2,8,2,7,7,4,2,12,4,7,4,7,2,10,4,9,4,4,2,13,2,4,7,11,4,8,

%U 2,7,4,8,2,15,2,4,7,7,4,8,2,12,8,4,2,13,4,4,4,9,2,13

%N Number of ordered pairs, (s,t), 1 <= s <= t, such that (t^s) | n.

%F a(n) = Sum_{(t^s)|n, 1<=s<=t<=n} 1.

%e a(9) = 4; The ordered pairs are (1,1), (1,3), (1,9), (2,3).

%e a(36) = 12; The ordered pairs are (1,1), (1,2), (1,3), (1,4), (1,6), (1,9), (1,12), (1,18), (1,36), (2,2), (2,3), (2,6).

%K nonn

%O 1,2

%A _Wesley Ivan Hurt_, Feb 14 2022