A263342 - OEIS

A263342

Irregular triangle read by rows: T(n,k) is the number of unlabeled graphs with n vertices containing exactly k non-isomorphic induced subgraphs, 1 <= n <= k < A370001(n).

1, 2, 2, 2, 2, 2, 5, 2, 2, 0, 1, 8, 4, 10, 7, 2, 2, 0, 0, 4, 4, 6, 6, 14, 16, 14, 22, 16, 20, 16, 10, 4, 2, 2, 0, 0, 0, 0, 4, 4, 4, 10, 8, 8, 16, 10, 20, 32, 42, 36, 40, 48, 74, 56, 68, 76, 60, 74, 72, 60, 72, 64, 26, 34, 14, 8, 2

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

Row sums give A000088, n >= 1.

There are at most A000171(n) odd terms in the n-th row, because complementary graphs have the same number of induced subgraphs. - Pontus von Brömssen, Mar 09 2024

LINKS

Pontus von Brömssen, Table of n, a(n) for n = 1..279 (rows n = 1..9)

FindStat - Combinatorial Statistic Finder, The number of induced subgraphs.

FORMULA

T(n,n) = 2 for n >= 2, because the empty graph and the complete graph are the only n-vertex graphs having only n non-isomorphic induced subgraphs. - Pontus von Brömssen, Mar 09 2024

EXAMPLE

Triangle begins:

2,2;

2,2,5,2;

2,0,1,8,4,10,7,2;

2,0,0,4,4,6,6,14,16,14,22,16,20,16,10,4,2;

...

CROSSREFS

Cf. A000088, A000171, A370001.

Sequence in context: A152659 A180214 A329438 * A089452 A162487 A215924

Adjacent sequences: A263339 A263340 A263341 * A263343 A263344 A263345

KEYWORD

nonn,tabf

AUTHOR

Christian Stump, Oct 15 2015

EXTENSIONS

a(34) and beyond from Pontus von Brömssen, Mar 09 2024

STATUS

approved