A128984 Degree of the special subgraph of Cayley graph constructed using the special (123)-avoiding and (132)-avoiding permutation patterns as generators.

2, 4, 6, 10, 12, 16, 18, 22, 28, 30, 36, 40, 42, 46, 50, 52, 56, 58, 60, 66, 70, 72, 76, 78, 82, 86, 88, 90, 96, 100, 102, 106, 110, 112, 116, 118, 122, 128, 130, 136, 140, 142, 146, 148, 150, 156, 160, 166, 170, 172, 178, 180, 182, 186, 190, 192, 196, 198, 200, 202

Offset

3,1

Comments

This sequence is constructed using a special veriety of subgraphs of Cayley graphs in order for a study of the degree/diameter problem.

References

Ibrahim A.A. and Audu M.S.(2005) Some Group Theoretic Properties of Certain Class of (123) and (132)-Avoiding Patterns of Numbers: An Enumeration Scheme: An enumeration Scheme, African Journal of Natural Sciences, Vol. 8:79-84

Ibrahim A.A. (2006) A Counting Scheme And Some Algebraic Properties of A Class of Special Permutation Patterns. (in preparation)

Ibrahim A.A. (2005) On the Combinatorics of Succession In A 5-element Sample Abacus Journal of Mathematical Association of Nigeria Vol. 32, No. 2B:410-415

Links

Table of n, a(n) for n=3..62.

Formula

Recursion relation:f(0)=2, f(2)=4, f(3)=6, f(4)=12, f(5)=f(1)+f(2)+f(3)+f(4)/f(0), f(n)=f(n-1)+f(n-2)+f(n-3)+f(n-4)-f(n-5)/f(0)-f(n-5), n>5 and provided the difference between consecutive numbers (before and at the start of the addition) does not exceed four digits. If however, this difference (m-(m-1)<=4 the f(n)=f(n-1)+f(n-2)+f(n-3)+f(n-4)/f(0)-f(n-4). [Indices need to be changed to match the offset. - R. J. Mathar, Dec 04 2011]

Crossrefs

Cf. A123642, A128929.

Sequence in context: A249434 A249425 A085477 * A249427 A075728 A146886

Adjacent sequences: A128981 A128982 A128983 * A128985 A128986 A128987

Keyword

nonn,uned

Author

Aminu Alhaji Ibrahim, Apr 30 2007

Extensions

An obviously incorrect prime formula deleted. - R. J. Mathar, Dec 04 2011

Status

approved