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 A220570 #34 Jan 22 2021 20:29:54 %S A220570 1,2,3,4,5,6,9,11,17,19,23,25,29,37,41,47,49,53,59,61,67,71,79,83,89, %T A220570 97,101,103,107,109,113,131,137,139,149,151,163,167,169,173,179,181, %U A220570 191,193,197,199,223,227,229,233,239,251,257,263,269,271,277,281 %N A220570 Numbers that are not Brazilian numbers. %C A220570 From _Bernard Schott_, Apr 23 2019: (Start) %C A220570 The terms of this sequence are: %C A220570 - integer 1 %C A220570 - oblong semiprime 6, %C A220570 - primes that are not Brazilian, they are in A220627, and, %C A220570 - squares of all the primes, except 121 = (11111)_3. %C A220570 So there is an infinity of integers that are not Brazilian numbers. (End) %C A220570 This sequence has density 0 as A125134(n) ~ n where A125134 is the complement of this sequence. - _David A. Corneth_, Jan 22 2021 %D A220570 Pierre Bornsztein, "Hypermath", Vuibert, Exercise a35, page 7. %H A220570 David A. Corneth, <a href="/A220570/b220570.txt">Table of n, a(n) for n = 1..10000</a> (first 1000 terms from T. D. Noe) %H A220570 Bernard Schott, <a href="/A125134/a125134.pdf">Les nombres brésiliens</a>, Quadrature, no. 76, avril-juin 2010, &6 page 36; included here with permission from the editors of Quadrature. %e A220570 25 is a member because it's not possible to write 25=(mm...mm)_b where b is a natural number with 1 < b < 24 and 1 <= m < b. %o A220570 (PARI) for(n=1,300,c=0;for(b=2,n-2,d=digits(n,b);if(vecmin(d)==vecmax(d),c=n;break);c++);if(c==max(n-3,0),print1(n,", "))) \\ _Derek Orr_, Apr 30 2015 %Y A220570 Cf. A125134 (Brazilian numbers), A190300 (composite numbers not Brazilian), A258165 (odd numbers not Brazilian), A220627 (prime numbers not Brazilian). %K A220570 nonn,easy,base %O A220570 1,2 %A A220570 _Bernard Schott_, Dec 16 2012