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 A073968 Number of strings of length n over Z_5 with trace 1 and subtrace 2. 7
 0, 0, 1, 20, 125, 650, 3150, 15625, 78000, 390625, 1952500, 9762500, 48815625, 244125000, 1220703125, 6103593750, 30517656250, 152587890625, 762939062500, 3814697265625, 19073484375000, 95367421875000, 476837119140625, 2384185742187500, 11920928955078125 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS Same as the number of strings of length n over Z_5 with: trace 2 and subtrace 3, trace 3 and subtrace 3, or trace 4 and subtrace 2. Same as the number of strings of length n over GF(5) with: trace 1 and subtrace 2, trace 2 and subtrace 3, trace 3 and subtrace 3, or trace 4 and subtrace 2. LINKS Max Alekseyev, PARI/GP scripts for miscellaneous math problems FORMULA a(n; t, s) = a(n-1; t, s) + a(n-1; t+4, s+4t+1) + a(n-1; t+3, s+3t+4) + a(n-1; t+2, s+2t+4) + a(n-1; t+1, s+t+1). Empirical g.f.: -x^3*(25*x^4-50*x^3+40*x^2-10*x-1) / ((5*x-1)*(5*x^2-1)*(25*x^4-25*x^3+15*x^2-5*x+1)). - Colin Barker, Nov 26 2014 EXAMPLE a(3;1,2)=1 since the one 5-ary string of trace 1, subtrace 2 and length 3 is { 222 }. CROSSREFS Cf. A073963, A073964, A073965, A073966, A073967, A073969, A073970. Sequence in context: A249709 A250648 A250421 * A219710 A263229 A125330 Adjacent sequences:  A073965 A073966 A073967 * A073969 A073970 A073971 KEYWORD easy,nonn AUTHOR Frank Ruskey and Nate Kube, Aug 15 2002 EXTENSIONS Terms a(11) onward from Max Alekseyev, Apr 09 2013 STATUS approved

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Last modified August 18 11:47 EDT 2022. Contains 356212 sequences. (Running on oeis4.)