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 A180169 #14 Jun 29 2025 21:30:40 %S A180169 1,3,4,8,1296,32,46656,128,256,512,1024,362797056,4096,8192,16384, %T A180169 32768,65536,131072,262144,524288,1048576,2097152,4194304,8388608, %U A180169 16777216,33554432,67108864,134217728,268435456,536870912,1073741824,2147483648 %N A180169 Sigma(A180162(n)), where A180162(n) is the smallest N such that sigma(N) is an n-th power, or 0 if no such N can be found. %H A180169 Ray Chandler, <a href="/A180169/b180169.txt">Table of n, a(n) for n = 0..469</a> %F A180169 Empirical o.g.f.: (-1-1*x+2*x^2-1280*x^4+2560*x^5-46592*x^6+93184*x^7-362795008*x^11+725590016*x^12)/(2*x-1). - Simon Plouffe, Feb 26 2011. %e A180169 A180162(4)=510 and so A180169(4)=sigma(510)=2^4*3^4. %Y A180169 Cf. A065496, A000203, A180162. %K A180169 easy,nonn %O A180169 0,2 %A A180169 _Walter Kehowski_, Aug 14 2010 %E A180169 a(23) onwards from _Ray Chandler_, Aug 20 2010