A355628 a(n) is the number of positive integers p that can be written as p = Product_{i = 1..n} (3 + 1/t_i) with integers t_i >= 2.

0, 2, 7, 25, 96, 364, 1344, 4921

Offset

1,2

Links

Table of n, a(n) for n=1..8.

Example

a(1) = 0 because (3 + 1/t_1) is not integer for t_1 >= 2.
a(2) = 2 because 10 = (3 + 1/4) * (3 + 1/13) and 11 = (3 + 1/2) * (3 + 1/7) and no other positive integer p can be written as p = (3 + 1/t_1) * (3 + 1/t_2) with integers t_1, t_2 >= 2, cf. A355626.

Prog

(PARI) See A355626.

Crossrefs

Cf. A355626, A355627, A355629, A355630, A355631.

Sequence in context: A150455 A150456 A150457 * A276903 A150458 A150459

Adjacent sequences: A355625 A355626 A355627 * A355629 A355630 A355631

Keyword

hard,more,nonn

Author

Markus Sigg, Jul 15 2022

Status

approved