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 A126663 #8 Nov 07 2020 15:57:25 %S A126663 1,0,2,2,2,2,4,6,8,2,6,10,12,6,10,16,10,6,8,10,2,18,10,14,26,30,24,26, %T A126663 14,16,18,16,28,34,16,14,36,42,6,50,20,2,24,48,20,24,58,16,44,42,48, %U A126663 26,30,60,70,46,30,28,24,20,80,30,34,72,12,62,84,52,36,64,12,78,36,56,96 %N A126663 Absolute difference between largest prime factors of two successive semiprimes. %C A126663 Absolute first difference of A084127. %e A126663 a(1) = 1 because 4 = 2*2 and 6 = 2*3 so 3 - 2 = 1; %e A126663 a(2) = 0 because 6 = 2*3 and 9 = 3*3 so 3 - 3 = 0; %e A126663 a(3) = 2 because 9 = 3*3 snd 10 = 2*5 so 5 - 3 = 2. %t A126663 Select[ FactorInteger[ Range[300]], Total[#[[All, 2]]] == 2 &][[All, -1, 1]] // Differences // Abs (* _Jean-François Alcover_, Dec 03 2013 *) %t A126663 Abs[#[[1]]-#[[2]]]&/@(Partition[FactorInteger[#][[-1,1]]&/@Select[ Range[ 300],PrimeOmega[#]==2&],2,1]) (* _Harvey P. Dale_, Nov 07 2020 *) %Y A126663 Cf. A001358, A006530, A084127. %K A126663 easy,nonn %O A126663 1,3 %A A126663 _Giovanni Teofilatto_, Mar 23 2007 %E A126663 Edited and extended by _Ray Chandler_, Mar 25 2007