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 A201018 #17 Feb 16 2025 08:33:16 %S A201018 15,35,51,57,75,115,135,153,175,315,351,355,395,511,513,517,531,535, %T A201018 539,553,575,579,597,715,755,759,795,935,957,975,1115,1135,1157,1175, %U A201018 1315,1351,1355,1359,1395,1513,1517,1535,1539,1557,1575,1593,1715,1751,1755,1795 %N A201018 Composite numbers whose multiplicative digital root is 5. %C A201018 Complement of A201017 with respect to A034052. %H A201018 Harvey P. Dale, <a href="/A201018/b201018.txt">Table of n, a(n) for n = 1..1000</a> %H A201018 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/MultiplicativeDigitalRoot.html">Multiplicative Digital Root</a> %e A201018 Composite number 153 is in the sequence because 1*5*3=15, 1*5=5. %t A201018 mdr5Q[n_]:=NestWhile[Times@@IntegerDigits[#]&,n,#>9&]==5; Select[Range[1800], CompositeQ[ #] &&mdr5Q[#]&] (* _Harvey P. Dale_, Dec 19 2023 *) %Y A201018 Cf. A201017 (primes whose multiplicative digital root is 5), A034052 (numbers whose multiplicative digital root is 5). %K A201018 nonn,base %O A201018 1,1 %A A201018 _Jaroslav Krizek_, Nov 25 2011