OFFSET
0,6
COMMENTS
n=14 is the unique fixed point of the sequence. - Gergely Földvári, Sep 22 2025
LINKS
EXAMPLE
a(9) = 4 because we have [7, 2], [5, 4], [4, 5] and [2, 7].
MAPLE
a:= proc(n) local b, l; l, b:= numtheory[divisors](n),
proc(m, i, p) option remember; `if`(m=0, p!, `if`(i<2, 0,
b(m, i-1, p)+`if`(i>m or i in l, 0, b(m-i, i-1, p+1))))
end; forget(b): b(n, n-1, 0)
end:
seq(a(n), n=0..63); # Alois P. Heinz, Feb 04 2020
MATHEMATICA
a[n_] := Module[{b, l = Divisors[n]}, b[m_, i_, p_] := b[m, i, p] = If[m == 0, p!, If[i < 2, 0, b[m, i - 1, p] + If[i > m || MemberQ[l, i], 0, b[m - i, i - 1, p + 1]]]]; b[n, n - 1, 0]];
a /@ Range[0, 63] (* Jean-François Alcover, Nov 30 2020, after Alois P. Heinz *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Feb 04 2020
STATUS
approved