A368791 a(n) = A008544(n) * Sum_{k=0..n} 1/A008544(k).

1, 3, 16, 129, 1420, 19881, 337978, 6759561, 155469904, 4042217505, 117224307646, 3751177844673, 131291224563556, 4989066533415129, 204551727870020290, 9000276026280892761, 423012973235201959768, 21150648661760097988401, 1120984379073285193385254

Offset: 0

Author

Seiichi Manyama, Jan 05 2024

Keywords

• nonn
• easy

Crossrefs

Row sums of A112333.

Cf. A008544, A368790.

Programs

PARI

a008544(n) = prod(k=1, n, 3*k-1);
a(n) = a008544(n)*sum(k=0, n, 1/a008544(k));

Formula

a(n) = (3*n-1) * a(n-1) + 1.