A054926 Number of connected unlabeled graphs with n nodes and floor(n*(n-1)/4) edges.

1, 0, 0, 2, 5, 19, 132, 1579, 33366, 1343120, 105723785, 15968704512, 4520384306832, 2402302590759788, 2425409960013204929, 4647586298937784001491, 16787189663016572148130262, 114715448859703502223876433517

Offset

1,4

Links

Table of n, a(n) for n=1..18.

V. A. Liskovets, Some easily derivable sequences, J. Integer Sequences, 3 (2000), #00.2.2.

Formula

a(n) = A054924(n, floor(n*(n-1)/4) ).

Crossrefs

Sequence in context: A365435 A273280 A272906 * A002786 A304982 A039719

Adjacent sequences: A054923 A054924 A054925 * A054927 A054928 A054929

Keyword

nonn,easy

Author

N. J. A. Sloane, May 24 2000

Extensions

Description corrected by David Wasserman, Mar 05 2002

Status

approved