A166680 a(n) = n*(a(n-1)-4), a(0) = 1.

1, -3, -14, -54, -232, -1180, -7104, -49756, -398080, -3582756, -35827600, -394103644, -4729243776, -61480169140, -860722368016, -12910835520300, -206573368324864, -3511747261522756, -63211450707409680

Offset: 0

Author

Philippe Deléham, Oct 18 2009

Keywords

• easy
• sign

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..200

Crossrefs

Cf. A000142, A166554, A165793, A165814.

Programs

Mathematica

RecurrenceTable[{a[0]==1,a[n]==n(a[n-1]-4)},a,{n,20}] (* Harvey P. Dale, Apr 18 2014 *)
FoldList[#1*#2 - 4 #2 &, 1, Range[50]] (* G. C. Greubel, May 23 2016 *)

Formula

a(n) = n! - 4*floor(e*n!) + 4, n>0. - Gary Detlefs, Jun 19 2010