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 A286652 #17 Jun 02 2017 00:42:51 %S A286652 1,2,6,30,42,66,78,210,330,390,462,510,546,570,690,714,798,858,870, %T A286652 930,966,1050,1110,1122,1218,1230,1254,1290,1302,1326,1410,1470,1482, %U A286652 1518,1554,1590,1650,1722,1770,1794,1806,1830,1914,1950,1974,2010,2046,2130 %N A286652 Unitary practical numbers: numbers n such that every 1 <= k <= usigma(n) is a sum of distinct unitary divisors of n. %C A286652 The unitary version of A005153. The squarefree terms of both sequences are the same, A265501. The nonsquarefree terms of this sequence are in A287173. %H A286652 Amiram Eldar, <a href="/A286652/b286652.txt">Table of n, a(n) for n = 1..1000</a> %t A286652 usigma[n_] := Block[{d = Divisors[n]}, Plus @@ Select[d, GCD[#, n/#] == 1 &]]; uPracticalQ[n_] := Module[{f, p, e, prod = 1, ok = True}, If[n < 1 || (n > 1 && OddQ[n]), False, If[n == 1, True, f = FactorInteger[n]; {p, e} = Transpose[f]; r = Sort[p^e]; Do[If[r[[i]] > 1 + usigma[prod], ok = False; Break[]]; prod = prod*r[[i]], {i, Length[p]}]; ok]]]; Select[ Range[100000], uPracticalQ] %Y A286652 Cf. A005153, A034448, A265501, A287173. %K A286652 nonn %O A286652 1,2 %A A286652 _Amiram Eldar_, May 27 2017