A394573 Number of graphs with n vertices that have no induced regular subgraph of order 4.

1, 2, 4, 7, 12, 12, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

Offset

1,2

Comments

a(n)=0 for all n>7.

Links

Table of n, a(n) for n=1..85.

Paul W. Dyson and Brendan D. McKay, Ramsey numbers for regular induced subgraphs, arXiv:2604.08215 [math.CO] (2026).

Paul Dyson and Brendan McKay, Ramsey Graphs (section Regular induced subgraphs)

S. Fajtlowicz, T. McColgan, T. Read, and W. Staton, Ramsey numbers for induced regular subgraphs, Ars Combinatoria, 39 (1995) 149-154.

Mathematica

PadRight[{1, 2, 4, 7, 12, 12, 2}, 100] (* Paolo Xausa, Apr 10 2026 *)

Crossrefs

Cf. A394400 (for order 4 or greater), A394539 (order 5), A394462 (order 6), A394930 (order 7).

Sequence in context: A267699 A384378 A193841 * A052474 A033054 A396011

Adjacent sequences: A394569 A394571 A394572 * A394574 A394575 A394576

Keyword

nonn

Author

Brendan McKay, Mar 25 2026

Status

approved