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A073959 Number of strings over Z_4 of length n with trace 1 and subtrace 2. +0
11
0, 2, 6, 16, 56, 192, 896, 4096, 17536, 69632 (list; graph; listen)
OFFSET

1,2

COMMENT

a(n; 1,2) = a(n; 3,2) where S(n; t,s) is the number of length n 4-ary strings whose digits sum to t mod 4 and whose sum of products of all pairs of digits sum to s mod 4.

Same as number of strings over Z_4 of length n with trace 3 and subtrace 2.

LINKS

F. Ruskey, Strings over Z_4 of given Trace and Subtrace

FORMULA

a(n; t, s) = a(n-1; t, s) + a(n-1; t+3, s+3t+1) + a(n-1; t+2, s+2t) + a(n-1; t+1, s+t+1) where t is the trace and s is the subtrace.

CROSSREFS

Cf. A073953, A068711, A073955, A068777, A068786, A068778, A068788, A068789, A073962.

Sequence in context: A045696 A091217 A068787 this_sequence A006820 A131385 A027742

Adjacent sequences: A073956 A073957 A073958 this_sequence A073960 A073961 A073962

KEYWORD

easy,nonn

AUTHOR

Frank Ruskey, Nate Kube (fruskey(AT)cs.uvic.ca), Aug 15 2002

EXTENSIONS

Edited by njas at the suggestion of Andrew Plewe, May 20 2007

page 1

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Last modified July 26 13:41 EDT 2008. Contains 142293 sequences.


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