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 A055240 #14 Jan 10 2024 04:55:52 %S A055240 0,0,0,0,0,0,0,0,0,0,1,0,1,0,0,0,3,0,3,0,1,1,6,0,3,1,2,0,7,0,7,1,4,4, %T A055240 7,0,9,4,6,1,11,0,13,2,3,6,17,0,11,3,8,3,18,2,13,3,11,9,22,0,18,9,8,4, %U A055240 15,1,23,8,16,5,24,1,24,12,11,8,24,4,29,4,15,14,31,1,22,14,21,8,34,1,23 %N A055240 Number of bases in which n is not divisible by any of its digits. %H A055240 Robert Israel, <a href="/A055240/b055240.txt">Table of n, a(n) for n = 1..10000</a> %e A055240 a(27)=2 because it is written as 27 in base 10 and 25 in base 11 and 27 is not divisible by 2, 5 or 7. %p A055240 f:= proc(n) %p A055240 nops(select(b -> not ormap(d -> d <> 0 and n mod d = 0, convert(n,base,b)), [$3 .. (n-1)/2])) %p A055240 end proc: %p A055240 map(f, [$1..100]); # _Robert Israel_, Jan 09 2024 %Y A055240 Cf. A055238, A055239, A055241, A055242. %K A055240 base,nonn,look %O A055240 1,17 %A A055240 _Henry Bottomley_, May 04 2000