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 A073494 #9 Dec 21 2013 05:52:34 %S A073494 110,130,170,182,190,220,230,238,260,266,273,290,310,322,340,357,364, %T A073494 370,374,380,399,406,410,418,430,434,440,460,470,476,483,494,506,518, %U A073494 520,530,532,546,550,561,574,580,590,598,602,609,610,620,627,638,644 %N A073494 Numbers having exactly two prime gaps in their factorization. %C A073494 A073490(a(n)) = 2. %H A073494 Reinhard Zumkeller, <a href="/A073494/b073494.txt">Table of n, a(n) for n = 1..10000</a> %e A073494 220 is a term, as 220 = 2*2*5*11 with two gaps: between 2 and 5 and between 5 and 11. %t A073494 pa[n_, k_] := If[k == NextPrime[n], 0, 1]; Select[Range[645], Total[pa @@@ Partition[First /@ FactorInteger[#], 2, 1]] == 2 &] (* _Jayanta Basu_, Jul 01 2013 *) %o A073494 (Haskell) %o A073494 a073494 n = a073494_list !! (n-1) %o A073494 a073494_list = filter ((== 2) . a073490) [1..] %o A073494 -- _Reinhard Zumkeller_, Dec 20 2013 %Y A073494 Cf. A005117, A073492, A073493, A073495, A073488. %K A073494 nonn %O A073494 1,1 %A A073494 _Reinhard Zumkeller_, Aug 03 2002