S ( n -- Sn )

Vocabulary

project-euler.463

Inputs

n

an object

Outputs

Sn

an object

Definition

USING: combinators kernel math ;

IN: project-euler.463

MEMO:: S ( n -- Sn )
    n {
        { -1 [ 0 ] }
        { 0 [ 0 ] }
        { 1 [ 1 ] }
        [
            drop n 2 /i S n 1 + 2 /i S 2 * + n 1 - 2 /i S 3 * +
            n 1 + 4 /i S 2 * - n 1 - 4 /i S 4 * - n 3 - 4 /i
            S 2 * - 1 -
        ]
    } case ;