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 A039700 #26 Apr 26 2025 03:27:19 %S A039700 1,3,18,36,45,63,72,99,117,144,153,171,207,225,261,270,279,288,333, %T A039700 369,378,387,423,441,477,531,540,549,576,594,603,639,657,702,711,747, %U A039700 756,801,873,909,918,927,945,963,981,1017,1026,1080,1089,1125,1143,1152 %N A039700 Numbers k such that the largest power of 3 dividing k equals 3^omega(k). %C A039700 Here, "omega(k)" means the number of prime factors of k counted without multiplicity. - _Harvey P. Dale_, Sep 30 2015 %H A039700 Amiram Eldar, <a href="/A039700/b039700.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Harvey P. Dale) %e A039700 omega(18) = 2 and 9 = 3^2 is the largest power of 3 dividing 18, hence 18 is in the sequence. %t A039700 Select[Range[1200],IntegerExponent[#,3]==PrimeNu[#]&] (* _Harvey P. Dale_, Sep 30 2015 *) %o A039700 (PARI) isok(k) = valuation(k, 3) == omega(k); \\ _Amiram Eldar_, Apr 26 2025 %Y A039700 Cf. A001221 (omega), A038500, A023534 (similar for powers of 2). %K A039700 nonn %O A039700 1,2 %A A039700 _Benoit Cloitre_, Sep 04 2002