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 A353167 #25 Jul 23 2022 19:27:56 %S A353167 0,5,10,15,17,20,27,30,34,39,40,45,51,54,57,60,65,68,75,78,80,85,90, %T A353167 95,99,102,105,108,114,119,120,125,130,135,136,141,147,150,153,156, %U A353167 160,165,170,175,177,180,187,190,195,198,201,204,210,215,216,221,225,228,235 %N A353167 Polynomials over GF(2) that are divisible by (x+1)^2 = x^2+1, encoded as binary numbers. %C A353167 Terms of A048725, sorted. %C A353167 See also A001969 for those divisible by x+1 (and obviously the present sequence is a subsequence of that one). %C A353167 From _Kevin Ryde_, Jul 22 2022: (Start) %C A353167 Integers with an even number of 1-bits at even positions, and an even number of 1-bits at odd positions, and so all k with A355487(k) = 0. %C A353167 Among four integers 4*i ..4*i+3, exactly one is a term here so that a(n) can be calculated by appending two bits to n-1 to ensure the two 1-bit counts are even, so a(n) = 4*(n-1) + A355487(n-1). %C A353167 (End) %o A353167 (PARI) a(n) = n--; n<<2 + if(n,fold(bitxor,digits(n,4))); \\ _Kevin Ryde_, Jul 01 2022 %Y A353167 Cf. A001969, A048725. %Y A353167 Cf. A355487 (mod 4), A341389 (mod 2). %K A353167 nonn,easy %O A353167 1,2 %A A353167 _Jack Zhang_, Apr 28 2022 %E A353167 More terms from _David A. Corneth_, Apr 28 2022