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 A144181 #14 Aug 21 2016 11:10:09 %S A144181 1,1,3,9,11,17,35,57,91,161,275,457,779,1329,2243,3801,6459,10945, %T A144181 18547,31465,53355,90449,153379,260089,440987,747745,1267923,2149897, %U A144181 3645387,6181233,10481027,17771801,30134267,51096321,86639923,146908457,249101099 %N A144181 INVERT transform of A118434, = row sums of triangle A144182. %C A144181 A118434 = row sums of the self-inverse triangle A118433 (a generator for the Rao Uppuluri-Carpenter numbers, A000587). %C A144181 A144181 = row sums of triangle A144182. %H A144181 Colin Barker, <a href="/A144181/b144181.txt">Table of n, a(n) for n = 0..1000</a> %H A144181 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,2). %F A144181 Equals row sums of triangle A144182 and INVERT transform of A118434: (1, 0, 2, 4, -4, 0, -8, -16, 16, 0, 32,...). %F A144181 From _Colin Barker_, Aug 21 2016: (Start) %F A144181 a(n) = a(n-1)+2*a(n-3) for n>3. %F A144181 G.f.: (1+2*x^2+4*x^3) / (1-x-2*x^3). %F A144181 (End) %e A144181 a(3) = 9 = sum of row 3 terms, triangle A144182: (4 + 2 + 0 + 3). %o A144181 (PARI) Vec((1+2*x^2+4*x^3)/(1-x-2*x^3) + O(x^40)) \\ _Colin Barker_, Aug 21 2016 %Y A144181 Cf. A118434. %Y A144181 Cf. A144182, A000587. %K A144181 nonn,easy %O A144181 0,3 %A A144181 _Gary W. Adamson_, Sep 13 2008 %E A144181 More terms from _Alois P. Heinz_, May 23 2015