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 A075806 #17 Mar 10 2025 11:02:00 %S A075806 1,2,2,4,55,35,30,20,30,10,31,60,31,40,20,10,51,40,20,61,40,11,40,81, %T A075806 30,20,10,10,122,10,40,32,220,330,220,451,660,451,220,781,660,341,220, %U A075806 110,220,110,11,220,220,440,451,220,110,110,110,451,220,220,220,341 %N A075806 Differences between adjacent palindromic numbers which are products of an odd number of distinct primes. %H A075806 Paolo Xausa, <a href="/A075806/b075806.txt">Table of n, a(n) for n = 1..1000</a> %e A075806 a(1)=3-2=1, a(2)=5-3=2, a(5)=66-11=55. %p A075806 test := proc(n) local d; d := convert(n,base,10); return ListTools[Reverse](d)=d and numtheory[mobius](n)=-1; end; s := []; for n from 1 to 11000 do if test(n) then s := [op(s),n]; end; od; a := [op(2..-1,s)-op(1..-2,s)]; %t A075806 Differences[Select[Range[10000], PalindromeQ[#] && MoebiusMu[#] == -1 &]] (* _Paolo Xausa_, Mar 10 2025 *) %Y A075806 Cf. A037010. %Y A075806 First differences of A075800. %K A075806 nonn,base %O A075806 1,2 %A A075806 _Jani Melik_, Oct 13 2002 %E A075806 Edited by _Dean Hickerson_, Oct 21 2002