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 A369661 #18 Feb 10 2024 18:57:48 %S A369661 9,21,25,33,49,57,69,85,93,121,129,133,145,169,177,205,213,217,237, %T A369661 249,253,265,289,309,329,361,375,393,417,445,459,469,473,489,493,505, %U A369661 517,529,533,553,565,573,581,597,629,633,669,685,697,713,753,781,783,793,813,817,819,841,865,869,875,889,913,933,949,961 %N A369661 Numbers k whose arithmetic derivative k' is of the form 4m+2, and k' has an even number of prime factors. %C A369661 Equally, numbers k whose arithmetic derivative k' is congruent to 2 modulo 4 and A276085(k') is congruent to 3 modulo 4. %C A369661 Numbers k such that A003415(k) is in A369966. %C A369661 For all n >= 1, A003415((1/2)*A003415(a(n))) is odd. %H A369661 Antti Karttunen, <a href="/A369661/b369661.txt">Table of n, a(n) for n = 1..10000</a> %o A369661 (PARI) \\ See A369660. %Y A369661 Setwise difference A327862 \ A369662. %Y A369661 Cf. A003415, A369660 (characteristic function), A369966. %Y A369661 Subsequences: A108181, A369663 (terms of the form 4m+3). %K A369661 nonn %O A369661 1,1 %A A369661 _Antti Karttunen_, Feb 06 2024