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 A294028 #18 Sep 07 2023 12:50:24
%S A294028 49,77,121,203,319,413,679,721,749,841,869,1057,1211,1351,1393,1397,
%T A294028 1441,1639,1687,1757,1769,1883,2167,2189,2219,2359,2429,2581,2651,
%U A294028 2761,2959,3031,3073,3101,3227,3409,3437,3485,3487,3563,3899,4037,4039,4109,4279
%N A294028 Composite numbers k such that k | 1 - A078712(k).
%C A294028 A018187 (restricted Perrin pseudoprimes) is the intersection of A013998 (unrestricted Perrin pseudoprimes) with this sequence.
%H A294028 Amiram Eldar, <a href="/A294028/b294028.txt">Table of n, a(n) for n = 1..10000</a>
%H A294028 William Adams and Daniel Shanks, <a href="http://dx.doi.org/10.1090/S0025-5718-1982-0658231-9">Strong primality tests that are not sufficient</a>, Math. Comp. 39 (1982), 255-300.
%t A294028 a={}; b=-Drop[CoefficientList[Series[(2x+3)/(x^3-x-1), {x, 0, 10^4}], x] ,1];
%t A294028 Do[If[!PrimeQ[k]&&Divisible[b[[k]]+1,k],AppendTo[a,k]],{k, 2, Length[b]}]; a
%Y A294028 Cf. A001608, A013998, A018187, A078712.
%K A294028 nonn
%O A294028 1,1
%A A294028 _Amiram Eldar_, Oct 22 2017