A276636 Number of up-down sequences with 3 copies each of 1,2,...,n.

1, 0, 1, 12, 761, 87336, 18528505, 6376563600, 3338759427857, 2524750777586976, 2648982517454387281, 3733860677541032881728, 6885982148044369769847497, 16251753910337100552968630400

Offset: 0

Author

Alois P. Heinz, Sep 08 2016

Keywords

• nonn

Examples

			a(3) = 12: 121313232, 121323132, 121323231, 131213232, 132312132, 132323121, 231213132, 231213231, 231312132, 231323121, 232312131, 232313121.
a(4) = 761: 121213243434, 121214343423, 121313242434, 121313243424, ..., 343424121213, 343424121312, 343424131212, 343434121212.
		

Crossrefs

Column k=3 of A275784.