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 A284763 #18 Apr 08 2017 09:51:30 %S A284763 1,2,3,5,6,7,8,9,10,11,13,14,15,17,19,21,22,23,25,26,29,30,31,32,33, %T A284763 34,35,37,38,39,40,41,42,43,45,46,47,49,51,53,55,56,57,58,59,61,62,63, %U A284763 65,66,67,69,70,71,73,74,75,77,78,79,82,83,85,86,87,88,89 %N A284763 Numbers n such that A279513(n) is squarefree. %C A284763 Also numbers with no duplicate prime number in their prime tower factorization (see A182318 for the definition of the prime tower factorization of a number). %C A284763 This sequence contains the squarefree numbers (A005117); 8 = 2^3 is the first term in this sequence that is not squarefree. %C A284763 All terms belong to A144146; 81 = 3^2^2 is the first term of A144146 that is not in this sequence. %H A284763 Rémy Sigrist, <a href="/A284763/b284763.txt">Table of n, a(n) for n = 1..10000</a> %e A284763 8 = 2^3 belongs to this sequence. %e A284763 24 = 3*2^3 does not belong to this sequence. %o A284763 (PARI) a279513(n) = my (f=factor(n)); prod(i=1, #f~, f[i, 1]*a279513(f[i, 2])); %o A284763 isok(n) = issquarefree(a279513(n)); \\ _Michel Marcus_, Apr 08 2017 %Y A284763 Cf. A005117, A144146, A182318. %K A284763 nonn %O A284763 1,2 %A A284763 _Rémy Sigrist_, Apr 02 2017