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 A071320 #30 Jan 18 2023 03:25:03 %S A071320 844,1681,8523,8954,10050,10924,11322,17404,19940,22020,23762,24450, %T A071320 25772,27547,30923,30924,33172,34347,38724,39050,39347,40050,47673, %U A071320 47724,47825,49147,54585,55449,57474,58473,58849,58867,59924,62865 %N A071320 Least of four consecutive numbers which are cubefree and not squarefree, i.e., numbers k such that {k, k+1, k+2, k+3} are in A067259. %C A071320 The numbers of terms not exceeding 10^k, for k = 1, 2, ..., are 0, 0, 1, 4, 57, 555, 5492, 55078, 551443, 5512825, ... . Apparently, the asymptotic density of this sequence exists and equals 0.000551... . - _Amiram Eldar_, Jan 18 2023 %H A071320 Amiram Eldar, <a href="/A071320/b071320.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..5000 from Michael De Vlieger) %F A071320 A051903(k) = A051903(k+1) = A051903(k+2) = A051903(k+3) = 2 when k is a term. %e A071320 k = 844 is a term since 844 = 2^2*211, k+1 = 845 = 5*13^2, k+2 = 846 = 2*3^2*47, and k+4 = 847 = 7*11^2. %t A071320 With[{s = Select[Range[10^5], And[MemberQ[#, 2], FreeQ[#, k_ /; k > 2]] &@ FactorInteger[#][[All, -1]] &]}, Function[t, Part[s, #] &@ SequencePosition[t, {1, 1, 1}][[All, 1]]]@ Differences@ s] (* _Michael De Vlieger_, Jul 30 2017 *) %Y A071320 Subsequence of A067259, A071318 and A071319. %Y A071320 Cf. A051903, A063528. %K A071320 nonn %O A071320 1,1 %A A071320 _Labos Elemer_, May 29 2002