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 A175431 #12 Dec 20 2021 02:42:31 %S A175431 1,2,4,5,6,8,9,10,11,12,13,14,15,16,17,18,19,20,23,24,25,26,27,28,29, %T A175431 30,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53, %U A175431 54,55,56,57,58,59,60,61,62,63,64,65,67,68,69,71,72,73,74,75,76,77,78,79 %N A175431 Numbers m such that sigma(m) is not a nontrivial power, i.e., sigma(m) = A000203(n) is not equal a^b where a and b are greater than 1. %C A175431 Complement of A065496. %C A175431 A175432(a(n)) = 1 for n >= 1. %e A175431 Number 3 is not in the sequence because sigma(3) = 4 = 2^2. %Y A175431 Cf. A000203, A065496, A175432. %K A175431 nonn %O A175431 1,2 %A A175431 _Jaroslav Krizek_, May 10 2010 %E A175431 Extended by _Ray Chandler_, Aug 20 2010