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 A362545 #15 Feb 16 2025 08:34:05
%S A362545 1,13,81,477,2785,16237,94641,551613,3215041,18738637,109216785,
%T A362545 636562077,3710155681,21624372013,126036076401,734592086397,
%U A362545 4281516441985,24954506565517,145445522951121,847718631141213,4940866263896161,28797478952235757,167844007449518385,978266565744874557,5701755387019728961,33232265756373499213
%N A362545 Number of odd chordless cycles of length >4 in the (2n+1)-flower snark.
%C A362545 Sequence extended to n=0 using formula/recurrence.
%C A362545 The (2n)-flower graphs, which generalize the (2n+1)-flower snarks, have no odd chordless cycles of length >=4.
%H A362545 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/FlowerSnark.html">Flower Snark</a>
%H A362545 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/OddChordlessCycle.html">Odd Chordless Cycle</a>
%H A362545 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (7,-7,1).
%F A362545 a(n) = LucasL(2 n + 1, 2) - 1.
%F A362545 a(n) = 7*a(n-1) - 7*a(n-1) + a(n-2).
%F A362545 G.f.: (-1 - 6*x + 3*x^2)/((-1 + x)*(1 - 6*x + x^2)).
%t A362545 LucasL[2 Range[0, 20] + 1, 2] - 1
%t A362545 Table[LucasL[2 n + 1, 2] - 1, {n, 0, 20}]
%t A362545 LinearRecurrence[{7, -7, 1}, {1, 13, 81}, 20]
%t A362545 CoefficientList[Series[(-1 - 6 x + 3 x^2)/((-1 + x) (1 - 6 x + x^2)), {x, 0, 20}], x]
%Y A362545 Cf. A002203 (companion Pell numbers).
%K A362545 nonn
%O A362545 0,2
%A A362545 _Eric W. Weisstein_, Apr 24 2023