A054595
Number of labeled 2-connected minimally 2-edge-connected graphs by nodes.
Original entry on oeis.org
1, 3, 22, 255, 3321, 52948, 1064988, 25071525, 667694395, 20114706546, 678833013618, 25302305856919, 1033146095157645, 45956558123679960, 2213869047416018296, 114892917344393371209, 6396625360877830999983
Offset: 3
Sridar K. Pootheri (sridar(AT)math.uga.edu), Apr 14 2000
- S. K. Pootheri, Counting classes of labeled 2-connected graphs, M.S. Dissertation, University of Georgia, 2000.
- S. K. Pootheri, Counting classes of labeled 2-connected graphs, M.S. Thesis, University of Georgia, 2000. [Local copy]
- S. K. Pootheri, Characterizing and counting classes of unlabeled 2-connected graphs, Ph. D. Dissertation, University of Georgia, 2000.
- S. K. Pootheri, Characterizing and counting classes of unlabeled 2-connected graphs, Ph. D. Dissertation, University of Georgia, 2000. [Local copy]
A290011
Number of ways to connect n nodes with n+1 edges to form a 2-edge-connected graph.
Original entry on oeis.org
6, 85, 900, 9450, 104160, 1224720, 15422400, 207900000, 2993760000, 45924278400, 748280332800, 12913284384000, 235381386240000, 4520194398720000, 91233825306624000, 1931115968990208000, 42778526977105920000, 989887004576870400000, 23885015465274163200000
Offset: 4
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seq((n^2 + 2 *n - 18)* n!/24, n=6..30); # Robert Israel, Jul 19 2017
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Table[(n - 4) (n!/8) + (n (n - 1)/2 - 3) (n!/12), {n, 4, 22}] (* Michael De Vlieger, Jul 18 2017 *)
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a(n) = (n - 4)*(n!/8) + (n*(n - 1)/2 - 3)*(n!/12); \\ Michel Marcus, Jul 18 2017
Original entry on oeis.org
1, 4, 26, 281, 3602, 56550, 1121538, 26193063, 693887458, 20808594004, 699641607622, 26001947464541, 1059148042622186, 47015706166302146, 2260884753582320442, 117153802097975691651, 6513779162975806691634
Offset: 3
a(6) = 1 + 3 + 22 + 255 = 281 is prime.
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