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a(n) = Product_{i=0..n} (3*i+1)! / (n+i)!.
0

%I #4 May 25 2020 16:04:20

%S 1,12,420,35280,6486480,2473511040,1888413246720,2815188363187200,

%T 8043859365429888000,43422645527382401280000,

%U 437806134821131674998400000,8167684917019434265210752000000,279763767797866931083907001600000000,17478686582471797472931336490014720000000

%N a(n) = Product_{i=0..n} (3*i+1)! / (n+i)!.

%K nonn

%O 0,2

%A Christian Krattenthaler (kratt(AT)ap.UniVie.AC.AT)