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A073955 Number of strings over Z_4 of length n with trace 0 and subtrace 2. +0
12
0, 0, 0, 8, 40, 240, 1120, 4480, 17536, 65280 (list; graph; listen)
OFFSET

1,4

COMMENT

a(n; 0,2) where a(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.

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, A068777, A068786, A068778, A073959, A068788, A068789, A073962.

Sequence in context: A051199 A068774 A068775 this_sequence A117083 A007987 A092397

Adjacent sequences: A073952 A073953 A073954 this_sequence A073956 A073957 A073958

KEYWORD

easy,nonn

AUTHOR

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

EXTENSIONS

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

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Last modified July 26 23:19 EDT 2008. Contains 142293 sequences.


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