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 A180126 #9 Jan 05 2023 18:41:59 %S A180126 3,34,15530,151165607042 %N A180126 a(n) is the least k such that for numbers x >= k, PrimePi(n,x) > PrimePi(n-1,x), where PrimePi(n,x) is the number of n-almost-primes <= x. %C A180126 Note that a(n) is an n-almost-prime. An n-almost-prime is a number having exactly n prime factors (counted with multiplicity). So 1 is the only 0-almost-prime; 1-almost-primes are the usual prime numbers; 2-almost-primes are also called semiprimes. The first three terms are mentioned in A125149. %C A180126 For 2 <= n <= 4, the values for a(n)/a(n-1) (11.3, 456.8, 9733780.2) are each a little larger than A281889(n), "the median n-th least prime factor of the integers". - _Peter Munn_, Jan 04 2023 %Y A180126 Cf. A078840, A125149, A281889. %K A180126 bref,hard,more,nonn %O A180126 1,1 %A A180126 _T. D. Noe_, Aug 11 2010 %E A180126 Name edited by _Peter Munn_, Jan 04 2023