login
A339071
Triangle read by rows: T(n,k) is the number of unlabeled nonseparable (or 2-connected) graphs with n nodes and k edges (n >= 1, n-1 <= k <= n*(n-1)/2).
6
0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 2, 3, 2, 1, 1, 0, 1, 3, 9, 14, 12, 8, 5, 2, 1, 1, 0, 1, 4, 20, 50, 82, 94, 81, 59, 38, 20, 10, 5, 2, 1, 1, 0, 1, 6, 40, 161, 429, 780, 1076, 1197, 1114, 885, 622, 386, 215, 112, 55, 24, 11, 5, 2, 1, 1, 0, 1, 7, 70, 433, 1729, 4796
OFFSET
1,11
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..576 (rows 1..16, extracted from Robinson's tables)
R. W. Robinson, Tables
R. W. Robinson, Tables [Local copy, with permission]
EXAMPLE
Triangle T(n,k) begins:
======================================================
n/k | 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
----+-------------------------------------------------
1 | 0;
2 | 1;
3 | 0, 1;
4 | 0, 1, 1, 1;
5 | 0, 1, 2, 3, 2, 1, 1;
6 | 0, 1, 3, 9, 14, 12, 8, 5, 2, 1, 1;
...
CROSSREFS
Row sums are A002218.
Column sums are A010355.
Cf. A054923, A054924, A123534, A339070 (transpose), A339072.
Sequence in context: A327758 A110540 A346399 * A358478 A083475 A211994
KEYWORD
nonn,tabf
AUTHOR
Andrew Howroyd, Nov 23 2020
STATUS
approved