A341132 Number of partitions of n into 2 distinct prime powers (including 1).

1, 1, 2, 2, 2, 2, 3, 3, 3, 4, 3, 3, 3, 3, 3, 4, 3, 5, 4, 3, 2, 5, 3, 4, 4, 5, 3, 6, 3, 6, 5, 6, 4, 7, 2, 5, 4, 6, 3, 6, 3, 6, 5, 5, 2, 8, 3, 7, 4, 6, 2, 8, 3, 7, 4, 5, 2, 8, 3, 6, 4, 6, 3, 9, 2, 8, 5, 7, 2, 10, 3, 7, 6, 7, 3, 9, 2, 9, 4, 6, 4, 11, 3, 8, 4, 7, 3, 12

Offset: 3

Author

Ilya Gutkovskiy, Feb 05 2021

Keywords

• nonn

Crossrefs

Cf. A000961, A010055, A071330, A282062, A306433, A307726, A341140, A341141, A341142, A341143, A341144, A341145.

Programs

Maple

q:= proc(n) option remember; nops(ifactors(n)[2])<2 end:
b:= proc(n, i, t) option remember; `if`(n=0,
      `if`(t=0, 1, 0), `if`(i<1 or t<1, 0, b(n, i-1, t)+
      `if`(q(i), b(n-i, min(n-i, i-1), t-1), 0)))
    end:
a:= n-> b(n$2, 2):
seq(a(n), n=3..90);  # Alois P. Heinz, Feb 05 2021

Mathematica

q[n_] := q[n] = PrimeNu[n] < 2;
b[n_, i_, t_] := b[n, i, t] = If[n == 0,
     If[t == 0, 1, 0], If[i < 1 || t < 1, 0, b[n, i - 1, t] +
     If[q[i], b[n - i, Min[n - i, i - 1], t - 1], 0]]];
a[n_] := b[n, n, 2];
Table[a[n], {n, 3, 90}] (* Jean-François Alcover, Jul 13 2021, after Alois P. Heinz *)