A242569 n!-2n.

-1, -2, 0, 16, 110, 708, 5026, 40304, 362862, 3628780, 39916778, 479001576, 6227020774, 87178291172, 1307674367970, 20922789887968, 355687428095966, 6402373705727964, 121645100408831962, 2432902008176639960, 51090942171709439958, 1124000727777607679956, 25852016738884976639954, 620448401733239439359952

Offset

1,2

Comments

For n > 2, a(n) is the largest value of k such that (n!+k)/(n+k) is an integer.

For n > 2, a(n) is the largest value of k such that (n!+k)/(n+k) is prime.

For n > 1, a(n) is even.

Links

Table of n, a(n) for n=1..24.

Formula

a(n) = n!-2n.

Example

3!-2*3 = 0 so a(3) = 0.
4!-2*4 = 16 so a(4) = 16.
5!-2*5 = 110 so a(5) = 110.

Prog

(Python)
import math
{print(math.factorial(n)-2*n) for n in range(1, 25)}
(PARI) for(n=1, 25, print(n!-2*n))

Crossrefs

Cf. A000142, A242567, A242568.

Sequence in context: A345652 A009528 A178987 * A152154 A324665 A349036

Adjacent sequences: A242566 A242567 A242568 * A242570 A242571 A242572

Keyword

sign

Author

Derek Orr, May 17 2014

Status

approved