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 A212639 #12 Jul 14 2019 09:49:23 %S A212639 0,2,3,4,5,4,6,5,7,6,6,8,7,7,9,8,8,6,10,9,8,9,7,11,10,9,10,8,12,11,10, %T A212639 8,11,9,10,13,12,11,9,12,10,11,14,13,12,10,9,13,11,12,10,15,14,13,11, %U A212639 8,12,10,14,12,13,11,16,15,14,12,9,13,11,15,13,14,12 %N A212639 Number of prime factors of A181800(n) (n-th powerful number that is the first integer of its prime signature), counted with multiplicity. %C A212639 Every nonnegative integer n appears A002865(n) times. %H A212639 Amiram Eldar, <a href="/A212639/b212639.txt">Table of n, a(n) for n = 1..10000</a> %H A212639 Will Nicholes, <a href="http://willnicholes.com/math/primesiglist.htm">List of prime signatures</a> %F A212639 a(n) = A001222(A181800(n)). %e A212639 72 (2^3*3^2, or 2*2*2*3*3) has a total of 5 prime factors when repetitions are counted. Since 72 = A181800(8), a(8) = 5. %Y A212639 Cf. A181800, A001222, A212172, A212176, A212179, A212645. %K A212639 nonn %O A212639 1,2 %A A212639 _Matthew Vandermast_, Jun 09 2012