A327608 Number of parts in all twice partitions of n where the second partition is strict.

0, 1, 3, 8, 17, 34, 74, 134, 254, 470, 842, 1463, 2620, 4416, 7545, 12749, 21244, 34913, 57868, 93583, 151963, 244602, 391206, 620888, 987344, 1550754, 2435087, 3804354, 5920225, 9162852, 14179754, 21785387, 33436490, 51121430, 77935525, 118384318, 179617794

Offset: 0

Author

Alois P. Heinz, Sep 18 2019

Keywords

• nonn

Examples

			a(3) = 8 = 1+2+2+3 counting the parts in 3, 21, 2|1, 1|1|1.
		

Links

• Alois P. Heinz, Table of n, a(n) for n = 0..4000

Crossrefs

Cf. A000009, A000041, A270995, A327554, A327594, A327605, A327607.

Programs

Maple

g:= proc(n, i) option remember; `if`(i*(i+1)/2 f+
       [0, f[1]])(g(n-i, min(n-i, i-1)))))
    end:
b:= proc(n, i) option remember; `if`(n=0, [1, 0],
      `if`(i<2, 0, b(n, i-1)) +(h-> (f-> f +[0, f[1]*
       h[2]/h[1]])(b(n-i, min(n-i, i))*h[1]))(g(i$2)))
    end:
a:= n-> b(n$2)[2]:
seq(a(n), n=0..37);

Mathematica

g[n_, i_] := g[n, i] = If[i(i+1)/2 < n, 0, If[n == 0, {1, 0}, g[n, i - 1] + Function[f, f + {0, f[[1]]}][g[n - i, Min[n - i, i - 1]]]]];
b[n_, i_] := b[n, i] = If[n == 0, {1, 0}, If[i < 2, 0, b[n, i - 1]] + Module[{h, f}, h = g[i, i]; f = b[n - i, Min[n - i, i]] h[[1]]; f + {0, f[[1]] h[[2]]/h[[1]]}]];
a[n_] := b[n, n][[2]];
a /@ Range[0, 37] (* Jean-François Alcover, Dec 05 2020, after Alois P. Heinz *)