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A073948 Number of strings over Z_3 of length n with trace 0 and subtrace 1. 5
0, 0, 0, 6, 30, 90, 252, 756, 2268, 6642, 19602, 58806, 176904, 530712, 1592136, 4780782, 14351094, 43053282, 129146724, 387440172, 1162320516, 3486843450, 10460294154, 31380882462, 94143001680, 282429005040, 847287015120, 2541864234006, 7625599079310 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

Same as number of strings over GF(3) of length n with trace 0 and subtrace 1.

LINKS

Table of n, a(n) for n=1..29.

Max Alekseyev, PARI/GP scripts for miscellaneous math problems

F. Ruskey, Strings over Z_3 with given trace and subtrace

F. Ruskey, Strings over GF(3) with given trace and subtrace

Index entries for linear recurrences with constant coefficients, signature (6,-15,27,-36,27).

FORMULA

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

G.f.: -6q^4(q-1)/[(1-3q)(1+3q^2)(1-3q+3q^2)]. - Lawrence Sze, Oct 24 2004

CROSSREFS

Cf. A073947, A073949, A073950, A073951, A073952.

Sequence in context: A107394 A033487 A061138 * A101855 A101375 A074007

Adjacent sequences:  A073945 A073946 A073947 * A073949 A073950 A073951

KEYWORD

easy,nonn

AUTHOR

Frank Ruskey and Nate Kube, Aug 15 2002

EXTENSIONS

Terms a(21) onward from Max Alekseyev, Apr 09 2013

STATUS

approved

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Last modified November 12 19:25 EST 2019. Contains 329078 sequences. (Running on oeis4.)