login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A166680
a(n) = n*(a(n-1)-4), a(0) = 1.
1
1, -3, -14, -54, -232, -1180, -7104, -49756, -398080, -3582756, -35827600, -394103644, -4729243776, -61480169140, -860722368016, -12910835520300, -206573368324864, -3511747261522756, -63211450707409680
OFFSET
0,2
LINKS
FORMULA
a(n) = n! - 4*floor(e*n!) + 4, n>0. - Gary Detlefs, Jun 19 2010
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 *)
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Philippe Deléham, Oct 18 2009
STATUS
approved