A358241 Number of connected Dynkin diagrams with n nodes.

1, 3, 3, 5, 4, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4

Offset: 1

Author

Simon Burton, Jan 18 2023

Keywords

• nonn
• easy

Comments

The sequence of connected Dynkin diagrams proceeds as {A1}, {A2, B2, G2}, {A3, B3, C3}, {A4, B4, F4, C4, D4}, {A5, B5, C5, D5}, {A6, B6, C6, D6, E6}, {A7, B7, C7, D7, E7}, {A8, B8, C8, D8, E8}, {A9, B9, C9, D9}, ...

References

• R. W. Carter, Simple groups of Lie type. Vol. 22, John Wiley & Sons, 1989, p. 40.

Links

• Wikipedia, Dynkin diagram
• Index entries for linear recurrences with constant coefficients, signature (1).

Crossrefs

Cf. A060296, A374624.

Formula

a(n) = 4 for n > 8.

Extensions

a(9) corrected by Andrey Zabolotskiy, Jul 23 2024