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 A347202 #28 May 12 2025 14:01:02 %S A347202 1,2,4,8,9,15,16,18,21,25,27,30,32,33,35,36,39,42,45,49,50,51,54,55, %T A347202 57,60,63,64,65,66,69,70,72,75,77,78,81,84,85,87,90,91,93,95,98,99, %U A347202 100,102,105,108,110,111,114,115,117,119,120,121,123,125,126,128,129,130 %N A347202 Numbers whose number of odd divisors is not equal to 2. %C A347202 Numbers that are not products of an odd prime and a power of 2. %C A347202 Numbers k such that the symmetric representation of sigma(k) has a number of subparts not equal to 2. %H A347202 Robert Israel, <a href="/A347202/b347202.txt">Table of n, a(n) for n = 1..10000</a> %p A347202 filter:= proc(n) not isprime(n/2^padic:-ordp(n,2)) end proc: %p A347202 select(filter, [$1..200]); # _Robert Israel_, May 09 2025 %t A347202 A347202Q[k_] := !PrimeQ[k/2^IntegerExponent[k, 2]]; %t A347202 Select[Range[200], A347202Q] (* _Paolo Xausa_, May 12 2025 *) %o A347202 (PARI) isok(m) = sumdiv(m, d, d%2) != 2; \\ _Michel Marcus_, Aug 23 2021 %Y A347202 Members of A266531 (sorted), except the column 2. %Y A347202 Cf. A001227, A038550 (complement), A237593, A279387 (subparts). %K A347202 nonn %O A347202 1,2 %A A347202 _Omar E. Pol_, Aug 22 2021