OFFSET
1,16
FORMULA
a(1) = 1; a(n) = Sum_{d|n, n/d > 3} a(d).
EXAMPLE
a(20) = 3: 20 = 4*5 = 5*4.
MATHEMATICA
a[n_] := a[n] = If[n == 1, n, Sum[If[n/d > 3, a[d], 0], {d, Divisors[n]}]]; Table[a[n], {n, 1, 89}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Mar 15 2024
STATUS
approved