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!)
 A306207 a(n) = Sum_{k=0..n} (n^2)!/((n^2-n*k)!*k!^n). 2
 1, 2, 19, 9745, 768211081, 17406784944114721, 179762725526880242306609281, 1230064011299573560897489169488350806401, 7660929590740297929124296619236388608530015362840364161 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Seiichi Manyama, Table of n, a(n) for n = 0..26 FORMULA From Vaclav Kotesovec, Jan 29 2019: (Start) a(n) ~ (n^2)! / (n! * ((n-1)!)^n). a(n) ~ exp(n - 1/12) * n^(n^2 - n/2 + 1/2) / (2*Pi)^(n/2). (End) PROG (PARI) {a(n) = sum(k=0, n, (n^2)!/((n^2-n*k)!*k!^n))} CROSSREFS Cf. A206849, A227403, A306206. Sequence in context: A094663 A274762 A091688 * A073444 A301637 A210416 Adjacent sequences:  A306204 A306205 A306206 * A306208 A306209 A306210 KEYWORD nonn AUTHOR Seiichi Manyama, Jan 29 2019 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 7 22:29 EST 2019. Contains 329850 sequences. (Running on oeis4.)