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A073971
Number of strings of length n over Z_6 with trace 0 and subtrace 0.
23
1, 1, 3, 18, 126, 1008, 8100, 52488, 297432, 1679616, 9843120, 59058720, 358108128, 2176782336, 13162730688, 78976384128, 471877757568, 2820249944064, 16891882995456, 101361597378048, 608764662139392, 3656158440062976, 21947909832446976, 131687458994681856
OFFSET
1,3
FORMULA
a(n; t, s) = a(n-1; t, s) + a(n-1; t+5, s+5t+1) + a(n-1; t+4, s+4t+4) + a(n-1; t+3, s+3t+3) + a(n-1; t+2, s+2t+2) + a(n-1; t+1, s+t+1) where t is the trace and s is the subtrace.
KEYWORD
easy,nonn
AUTHOR
Frank Ruskey, Nate Kube, Aug 16 2002
EXTENSIONS
Terms a(11) onward from Max Alekseyev, Apr 09 2013
STATUS
approved