This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A255630 #22 Dec 19 2015 01:06:39
%S A255630 1,2,5,13,32,79,197,490,1217,3025,7520,18691,46457,115474,287021,
%T A255630 713413,1773248,4407559,10955357,27230458,67683593,168233257,
%U A255630 418157888,1039366555,2583432881,6421339426,15960778517,39671855677,98607729632
%N A255630 Number of n-length ternary words avoiding runs of zeros of length 1 (mod 3).
%H A255630 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (2,0,3).
%F A255630 a(n+3) = 2*a(n+2) + 3*a(n) with n > 0, a(0) = 1, a(2) = 2, a(3) = 5.
%F A255630 G.f.: ( -1-x^2 ) / ( -1+2*x+3*x^3 ). - _R. J. Mathar_, Aug 07 2015
%F A255630 a(n) = A099525(n)+A099525(n-2). - _R. J. Mathar_, Aug 07 2015
%t A255630 RecurrenceTable[{a[0] == 1, a[2] == 2, a[3] == 5, a[n] == 2* a[n - 1] + 3*a[n - 3]}, a[n], {n, 0, 29}]
%Y A255630 Cf. A254598, A254602, A255115, A255117, A254601, A254663.
%K A255630 nonn,easy
%O A255630 0,2
%A A255630 _Milan Janjic_, Feb 28 2015