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 A212179 #13 Jul 14 2019 08:34:32 %S A212179 0,1,1,1,1,2,1,2,1,2,2,1,2,2,1,2,2,3,1,2,2,2,3,1,2,2,2,3,1,2,2,3,2,3, %T A212179 2,1,2,2,3,2,3,2,1,2,2,3,3,2,3,2,3,1,2,2,3,4,2,3,2,3,2,3,1,2,2,3,4,2, %U A212179 3,2,3,2,3,1,2,3,2,3,4,2,3,3,2,3,2,3,1,4 %N A212179 Number of distinct prime factors of A181800(n) (n-th powerful number that is the first integer of its prime signature). %C A212179 Since each prime factor of A181800(n) divides A181800(n) at least twice, this is also the number of exponents > 2 in prime factorization of A181800(n). %C A212179 Length of row A181800(n) of table A212171 equals a(n) for n > 1. Row A181800(n) of table A212172 has the same length when n > 1 (length = 1 if n = 1). %H A212179 Amiram Eldar, <a href="/A212179/b212179.txt">Table of n, a(n) for n = 1..10000</a> %H A212179 Will Nicholes, <a href="http://willnicholes.com/math/primesiglist.htm">Prime Signatures</a> %F A212179 a(n) = A001221(A181800(n)) = A056170(A181800(n)). %e A212179 72 (2^3*3^2) has 2 distinct prime factors. Since 72 = A181800(8), a(8) = 2. %Y A212179 Cf. A181800, A001694, A025487, A212171, A212172, A212176. %K A212179 nonn %O A212179 1,6 %A A212179 _Matthew Vandermast_, Jun 04 2012