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Sequence is identical to its third differences in absolute values: a(n+k)=3a(n+k-1)-3a(n+k-2)+2a(n+k-3), k=0, 1, 2, 3, 4, a(n+5)=3a(n+4)-3a(n+3), n > 2.
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%I #8 Sep 23 2015 11:35:02

%S 1,2,3,5,10,21,43,86,129,215,430,903,1849,3698,5547,9245,18490,38829,

%T 79507

%N Sequence is identical to its third differences in absolute values: a(n+k)=3a(n+k-1)-3a(n+k-2)+2a(n+k-3), k=0, 1, 2, 3, 4, a(n+5)=3a(n+4)-3a(n+3), n > 2.

%C (6n+1)-th terms: 43, 43^2, 43^3, 43^4?

%H <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (0, 0, 0, 0, 0, 43).

%F 6n-th terms of a(n) opposite to the 6th of third differences. These terms are 21=3*7, 903=21*43, 38829=21*43^2.

%t LinearRecurrence[{0, 0, 0, 0, 0, 43},{1, 2, 3, 5, 10, 21},19] (* _Ray Chandler_, Sep 23 2015 *)

%K nonn

%O 0,2

%A _Paul Curtz_, Nov 13 2007