This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A299121 a(n) = Sum_{k=0..n} (k*(n-k))!. 0
 1, 2, 3, 6, 38, 1490, 443762, 965262242, 23539096637282, 4878608938121399042, 16752209028723653862101762, 531115497554502361264846265433602, 392660148984369152453298787770243889113602, 2811644066816242246665284589590844386691155533363202 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS FORMULA a(n) ~ sqrt(Pi) * n^(n^2/2 + 1) / (2^(n^2/2 + 1/2) * exp(n^2/4)) if n is even, and a(n) ~ sqrt(Pi) * n^(n^2/2 + 1/2) / (2^(n^2/2 - 1) * exp(n^2/4)) if n is odd. MATHEMATICA Table[Sum[(k*(n-k))!, {k, 0, n}], {n, 0, 14}] CROSSREFS Cf. A000142, A003149, A003422. Sequence in context: A299399 A173501 A018340 * A184716 A018354 A124045 Adjacent sequences:  A299118 A299119 A299120 * A299122 A299123 A299124 KEYWORD nonn AUTHOR Vaclav Kotesovec, Feb 03 2018 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 14 12:04 EST 2019. Contains 329979 sequences. (Running on oeis4.)