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%I #16 Jul 07 2023 14:46:12
%S 3,5,6,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,
%T 29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,
%U 52,53,54,55,56,57,58,59,60,61,62,63,64,65
%N Number of segments needed to draw the spiral of equilateral triangles with side lengths which follow the Padovan sequence.
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).
%F a(1)=3: a(2)=5: a(3)=6; for n>3, a(n)=n+4.
%t LinearRecurrence[{2,-1},{3,5,6,8,9},70] (* _Harvey P. Dale_, Dec 21 2018 *)
%o (PARI) a(n)=if(n>3,n+4,[3,5,6][n]) \\ _Charles R Greathouse IV_, Oct 27 2011
%Y Cf. Padovan sequence: A000931.
%K easy,nonn
%O 1,1
%A _Omar E. Pol_, Nov 04 2007, Nov 05 2007
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