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 A352218 #16 Dec 25 2024 04:04:14
%S A352218 0,1,1,1,2,1,2,1,2,3,2,2,3,2,2,3,4,3,2,3,4,3,2,3,5,4,4,3,3,5,4,4,3,3,
%T A352218 6,4,5,5,4,3,6,4,5,5,4,3,7,4,6,5,5,6,4,7,4,6,5,5,6,4,8,4,7,5,6,6,5,8,
%U A352218 7,4,7,5,6,6,5,9,7,4,8,5,7,6,6,9,7,5,8
%N A352218 a(n) = least k such that A003592(n) | 20^k.
%C A352218 Also, number of digits in the vigesimal (base 20) expansion of terminating unit fractions 1/A003592.
%D A352218 G. H. Hardy and E. M. Wright, An Introduction to the Theory of Numbers, Chapter IX: The Representation of Numbers by Decimals, Theorem 136. 8th ed., Oxford Univ. Press, 2008, 144-145.
%H A352218 Michael De Vlieger, <a href="/A352218/b352218.txt">Table of n, a(n) for n = 1..10212</a> (A003592(10212) = 20^50)
%H A352218 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Vigesimal.html">Vigesimal</a>.
%H A352218 Wikipedia, <a href="https://en.wikipedia.org/wiki/Vigesimal">Vigesimal</a>.
%e A352218 a(1) = 0 since A003592(1) = 1 | 20^0.
%e A352218 a(4) = 1 since A003592(4) = 5 | 20^1; 1/5 in base 20 = 0.4.
%e A352218 a(5) = 2 since A003592(5) = 8 | 20^2; 1/8 in base 20 = 0.2a, where "a" is digit 10, etc.
%t A352218 With[{nn = 360000}, Sort[Join @@ Table[{2^a*5^b, Max[Ceiling[a/2], b]}, {a, 0, Log2[nn]}, {b, 0, Log[5, nn/(2^a)]}]][[All, -1]] ]
%Y A352218 Cf. A003592, A086415, A117920.
%K A352218 nonn,easy,base
%O A352218 1,5
%A A352218 _Michael De Vlieger_, Mar 08 2022