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 A175432 #16 Nov 07 2017 18:32:13 %S A175432 1,1,2,1,1,1,3,1,1,1,1,1,1,1,1,1,1,1,1,1,5,2,1,1,1,1,1,1,1,1,5,1,1,1, %T A175432 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,1,1, %U A175432 1,2,1,1,1,1,1,1,1,1,1,1,2,1,1,1,1,1,1,1,1,1,1,1,7,2,1,1,1,1,1,1 %N A175432 a(n) = the greatest number k such that sigma(n) = m^k for any m >= 1 (sigma = A000203). %C A175432 a(A175431(n)) = 1 for n >= 1. %C A175432 a(A065496(n)) > 1 for n >= 1. %C A175432 It appears that the record values in this sequence, 1, 2, 3, 5, 7, 8, 9, 10, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, ..., is A180221 with a 1 prepended, at least through term #469. Is this a theorem? - _Ray Chandler_, Aug 20 2010 %H A175432 Antti Karttunen, <a href="/A175432/b175432.txt">Table of n, a(n) for n = 1..16384</a> %F A175432 a(n) = A052409(A000203(n)). - _N. J. A. Sloane_, Aug 19 2010 %F A175432 a(n) = log_A175433(n) [A000203(n)]. %e A175432 For n = 7, a(7) = 3 because sigma(7) = 8 = 2^3. %t A175432 Array[Apply[GCD, FactorInteger[DivisorSigma[1, #]][[All, -1]]] &, 105] (* _Michael De Vlieger_, Nov 05 2017 *) %o A175432 (PARI) a(n)=max(ispower(sigma(n)),1) \\ _Charles R Greathouse IV_, Feb 14 2013 %Y A175432 For locations of records see A169981. %Y A175432 Cf. A000203, A052409, A175433. %K A175432 nonn %O A175432 1,3 %A A175432 _Jaroslav Krizek_, May 10 2010