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 A075815 #11 Jan 28 2021 12:24:50 %S A075815 99,171,333,343,363,555,575,595,747,777,909,969,1001,1221,1331,1551, %T A075815 1771,3333,3553,5335,5445,5555,5665,5775,5885,5995,7337,7557,7667, %U A075815 7777,7887,9009,9339,9559,9669,9779,9889,11211,11511,11711,11811,12121 %N A075815 Palindromic odd composite numbers with an odd number of prime factors (counted with multiplicity). %H A075815 Harvey P. Dale, <a href="/A075815/b075815.txt">Table of n, a(n) for n = 1..1000</a> %e A075815 5445=3^2*5*11^2 and 5555=5*11*101 are palindromic, odd, composite and have an odd number of prime factors. %p A075815 test := proc(n) local d; d := convert(n,base,10); return ListTools[Reverse](d)=d and type(numtheory[bigomega](n),odd) and not isprime(n); end; a := []; for n from 1 to 13000 by 2 do if test(n) then a := [op(a),n]; end; od; a; %t A075815 Select[Range[9,13000,2],PalindromeQ[#]&&CompositeQ[#]&&OddQ[ PrimeOmega[ #]]&] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Jan 28 2021 *) %Y A075815 Cf. A046389. %K A075815 nonn,base %O A075815 1,1 %A A075815 _Jani Melik_, Oct 13 2002 %E A075815 Edited by _Dean Hickerson_, Oct 21 2002