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A108142 a[1] = 1; a[2] = 1; a[3] = 1; a[4] = 1; a[5] = 1; a[6] = 1; for n >= 7, a[n] = 6*a[n - 1] - 5*a[n - 2] - 4*a[n - 3] - 3*a[ n - 4] + 2*a[n - 5] + a[n - 6]; then take absolute values.

%I A108142 #9 Apr 25 2018 10:34:00
%S A108142 1,1,1,1,1,1,3,27,151,759,3679,17599,83767,397943,1889059,8964891,
%T A108142 42539855,201849743,957752095,4544385823,21562354767,102309686479,
%U A108142 485441784803,2303337053819,10928934112423,51855892302151
%N A108142 a[1] = 1; a[2] = 1; a[3] = 1; a[4] = 1; a[5] = 1; a[6] = 1; for n >= 7, a[n] = 6*a[n - 1] - 5*a[n - 2] - 4*a[n - 3] - 3*a[ n - 4] + 2*a[n - 5] + a[n - 6]; then take absolute values.
%C A108142 The 2nd countdown sequence.
%D A108142 Roger Bagula, Factoring Double Fibonacci Sequences, 2000
%H A108142 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (6, -5, -4, -3, 2, 1).
%t A108142 F[1] = 1; F[2] = 1; F[3] = 1; F[4] = 1; F[5] = 1; F[6] = 1; F[n__] := F[n] = 6*F[n - 1] - 5*F[n - 2] - 4*F[n - 3] - 3*F[ n - 4] + 2*F[n - 5] + F[n - 6] a = Table[Abs[F[n]], {n, 1, 50}]
%t A108142 LinearRecurrence[{6,-5,-4,-3,2,1},{1,1,1,1,1,1,3,27,151,759,3679,17599},30] (* _Harvey P. Dale_, Apr 25 2018 *)
%Y A108142 Cf. A056015, A056016.
%K A108142 nonn
%O A108142 1,7
%A A108142 _Roger L. Bagula_, Jun 05 2005
%E A108142 Edited by _N. J. A. Sloane_, Jun 08 2007