A068087 a(n) = n^(2*n-2).

1, 4, 81, 4096, 390625, 60466176, 13841287201, 4398046511104, 1853020188851841, 1000000000000000000, 672749994932560009201, 552061438912436417593344, 542800770374370512771595361, 629983141281877223603213172736, 852226929923929274082183837890625

Offset: 1

Author

Sharon Sela (sharonsela(AT)hotmail.com), May 06 2002

Keywords

• nonn
• easy

Comments

Number of spanning trees in the bipartite graph K(n,n). In general the number of spanning trees in the bipartite graph K(m,n) is m^(n-1) * n^(m-1).

Links

• Eric Weisstein's World of Mathematics, Complete Bipartite Graph
• Eric Weisstein's World of Mathematics, Spanning Tree

Crossrefs

a(n) = A000169(n)^2.

Cf. A069996, A001787, A072590, A294360.

Programs

PARI

a(n)=n^(2*n-2) \\ Charles R Greathouse IV, Mar 31 2016