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A185140
Irregular triangle E(n,g) counting not necessarily connected 4-regular simple graphs on n vertices with girth exactly g.
2
1, 1, 2, 5, 1, 16, 0, 58, 2, 264, 2, 1535, 12, 10755, 31, 87973, 220, 803973, 1606, 8020967, 16829, 86029760, 193900, 983431053, 2452820, 11913921910, 32670331, 1, 152352965278, 456028487, 2, 2050065073002, 6636066126, 8, 28466234288520, 100135577863, 131, 8020967, 16829
OFFSET
5,3
COMMENTS
The first column is for girth at least 3. The column for girth g commences when n reaches A037233(g).
FORMULA
The n-th row is the sequence of differences of the n-th row of A185340:
E(n,g) = A185340(n,g) - A185340(n,g+1), once we have appended 0 to each row of A185340.
Hence the sum of the n-th row is A185340(n,3) = A033301(n).
EXAMPLE
05: 1;
06: 1;
07: 2;
08: 5, 1;
09: 16, 0;
10: 58, 2;
11: 264, 2;
12: 1535, 12;
13: 10755, 31;
14: 87973, 220;
15: 803973, 1606;
16: 8020967, 16829;
17: 86029760, 193900;
18: 983431053, 2452820;
19: 11913921910, 32670331, 1;
20: 152352965278, 456028487, 2;
21: 2050065073002, 6636066126, 8;
22: 28466234288520, 100135577863, 131;
CROSSREFS
Initial columns of this triangle: A185143 (g=3), A185144 (g=4).
Sequence in context: A216962 A186756 A184940 * A111797 A122104 A216121
KEYWORD
nonn,hard,tabf
AUTHOR
Jason Kimberley, Jan 06 2013
STATUS
approved