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 A073772 #9 Jul 15 2024 02:36:55 %S A073772 0,0,-1,0,0,1,-1,-1,0,1,1,-1,0,-1,1,1,-1,0,1,1,1,-1,-1,2,2,-1,-1,1,1, %T A073772 1,2,-1,2,2,-1,-1,-1,1,1,1,2,-1,2,2,-1,2,2,2,-1,-1,2,-1,2,-1,2,2,-1,2, %U A073772 2,2,-1,-1,2,2,2,-1,2,3,-1,-1,2,2,2,-1,-1,1,1,1,1,-1,-1,3,3,3,3,-1,-1,2,2,2,-1,1,1,-1,3,3,3,3 %N A073772 Number of highly composite numbers (HCNs) between the n-th highly composite number k and 2*k if 2*k is a highly composite number, or -1 if 2*k is not a highly composite number. %C A073772 If 2*A002182(n) = A002182(m) then a(n) = m - n - 1; if 2*A002182(n) is not a highly composite number then a(n) = -1. The zero terms correspond to the terms of A072938, the negative terms correspond to the terms of A073771. The terms were determined by means of A. Flammenkamp's list (cf. Links). %H A073772 Achim Flammenkamp <a href="https://wwwhomes.uni-bielefeld.de/achim/highly.html">Highly Composite Numbers</a>. %e A073772 a(3) = -1 since 4 is the third highly composite number and 2*4 = 8 is not a highly composite number; a(6) = 1 since 24 is the sixth highly composite number, 2*24 = 48 is the eighth highly composite number and the highly composite number 36 is between them; a(13) = 0 since 360 is the 13th highly composite number, 2*360 = 720 is the 14th highly composite number and there is no highly composite number between them. %Y A073772 Cf. A002182, A072938, A073771. %K A073772 sign %O A073772 1,24 %A A073772 _Klaus Brockhaus_, Aug 19 2002