A193129 Number of spanning trees of the n-barbell graph.

1, 1, 1, 9, 256, 15625, 1679616, 282475249, 68719476736, 22876792454961, 10000000000000000, 5559917313492231481, 3833759992447475122176, 3211838877954855105157369, 3214199700417740936751087616, 3787675244106352329254150390625

Offset

0,4

Comments

a(n) = A000272(n)^2 for n>=0.

Links

M. F. Hasler, Table of n, a(n) for n = 0..32 (corrected by Georg Fischer, Jan 20 2019)

Eric Weisstein's World of Mathematics, Barbell Graph

Eric Weisstein's World of Mathematics, Spanning Tree

Formula

a(0)=1 and a(n)=n^(2n-4) for n>=1 (from the comment and the formula for A000272).

Mathematica

Table[n^(2 n - 4), {n, 3, 20}]

Prog

(PARI) A193129=n^(2*n-4) \\ M. F. Hasler, Apr 14 2015

Crossrefs

Cf. A000272.

Sequence in context: A212290 A296950 A025133 * A183493 A183424 A160073

Adjacent sequences: A193126 A193127 A193128 * A193130 A193131 A193132

Keyword

nonn

Author

Eric W. Weisstein, Jul 16 2011

Status

approved