A331928 Number of compositions (ordered partitions) of n into distinct proper divisors of n.
1, 0, 0, 0, 0, 0, 6, 0, 0, 0, 0, 0, 30, 0, 0, 0, 0, 0, 30, 0, 24, 0, 0, 0, 894, 0, 0, 0, 120, 0, 150, 0, 0, 0, 0, 0, 1134, 0, 0, 0, 864, 0, 30, 0, 0, 0, 0, 0, 11934, 0, 0, 0, 0, 0, 150, 0, 840, 0, 0, 0, 129438, 0, 0, 0, 0, 0, 126, 0, 0, 0, 0
Offset: 0
Keywords
Examples
a(6) = 6 because we have [3, 2, 1], [3, 1, 2], [2, 3, 1], [2, 1, 3], [1, 3, 2] and [1, 2, 3].
Programs
-
PARI
a(n)={if(n==0, 1, my(v=divisors(n)); subst(serlaplace((0*y) + polcoef(prod(i=1, #v-1, 1 + y*x^v[i] + O(x*x^n)), n)), y, 1))} \\ Andrew Howroyd, Feb 01 2020
Formula
a(n) = A331927(n) - 1 for n > 0.