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 A231271 #24 Aug 12 2024 09:35:22
%S A231271 1,5,7,9,13,17,23,29,31,37,41,49,53,61,71,73,85,89,97,101,103,109,113,
%T A231271 119,125,127,129,133,137,149,151,157,167,173,181,193,197,199,217,223,
%U A231271 229,233,241,249,257,263,269,277,281,293,311,313,317,321,325,337,341
%N A231271 Numbers k such that k and k+d are both odious (A000069) or both evil (A001969) for every divisor d of k.
%C A231271 A prime p is a term iff its binary expansion ends in odd number of 1's (A095283). All terms are in A079523.
%H A231271 Peter J. C. Moses, <a href="/A231271/b231271.txt">Table of n, a(n) for n = 1..10000</a>
%e A231271 The odious number k = 341 has divisors {1, 11, 31, 341}. Since the numbers 341 + 1 = 342, 341 + 11 = 352, 341 + 31 = 372, 341 + 341 = 682 are all odious, then 341 is a term.
%t A231271 odiousQ[n_] := OddQ[DigitCount[n, 2][[1]]];selQ[n_] := Length[Union[Map[odiousQ, Flatten[{n, Map[n+#&, Divisors[n]]}]]]] == 1; Select[Range[200], selQ] (* _Peter J. C. Moses_, Nov 08 2013 *)
%o A231271 (PARI) is(k) = {my(hw = hammingweight(k) % 2); fordiv(k, d, if(hammingweight(k+d) % 2 != hw, return(0))); 1;} \\ _Amiram Eldar_, Aug 12 2024
%Y A231271 Cf. A000069, A001969, A079523, A095283.
%K A231271 nonn,base
%O A231271 1,2
%A A231271 _Vladimir Shevelev_, Nov 06 2013
%E A231271 More terms from _Peter J. C. Moses_, Nov 08 2013