A003776 Number of 2-factors in P_5 X P_2n.

3, 54, 1140, 24360, 521064, 11146656, 238452456, 5101047216, 109123156248, 2334395822496, 49938107061384, 1068291209653392, 22853211220567416, 488882861126970624

Offset: 1

Author

Frans J. Faase

Keywords

• nonn

References

• F. Faase, On the number of specific spanning subgraphs of the graphs G X P_n, Ars Combin. 49 (1998), 129-154.

Links

• F. Faase, On the number of specific spanning subgraphs of the graphs G X P_n, Preliminary version of paper that appeared in Ars Combin. 49 (1998), 129-154.
• F. Faase, Counting Hamiltonian cycles in product graphs
• F. Faase, Results from the counting program

Formula

a(n) = 24a(n-1) - 57a(n-2) + 26a(n-3), n>3.

G.f.: 3x(1-5x)(1-x)/((1-2x)(1-22x+13x^2)). [From R. J. Mathar, Dec 16 2008]