cp's OEIS Frontend

A171607 Expressible as A*B^A in a nontrivial way.

%I A171607 #12 Feb 19 2017 22:29:42
%S A171607 8,18,24,32,50,64,72,81,98,128,160,162,192,200,242,288,324,338,375,
%T A171607 384,392,450,512,578,648,722,800,882,896,968,1024,1029,1058,1152,1215,
%U A171607 1250,1352,1458,1536,1568,1682,1800,1922,2048,2178,2187,2312,2450,2500,2592
%N A171607 Expressible as A*B^A in a nontrivial way.
%H A171607 Charles R Greathouse IV, <a href="/A171607/b171607.txt">Table of n, a(n) for n = 1..10000</a>
%H A171607 R. Munafo, <a href="https://mrob.com/pub/seq/cullen.html">Generalized Cullen and Woodall Numbers</a>
%F A171607 a(n) = 2n^2 - O(n^(5/3)). - _Charles R Greathouse IV_, Feb 19 2017
%e A171607 8=2*2^2. 24=3*2^3. 375=3*5^3.
%o A171607 (PARI) is(n)=if(n<8, return(0)); for(a=2,logint(n\2,2), if(n%a==0 && ispower(n/a,a), return(1))); 0 \\ _Charles R Greathouse IV_, Feb 19 2017
%o A171607 (PARI) list(lim)=my(v=List()); if(lim<8,return([])); for(a=2,logint(lim\2,2), for(b=2,sqrtnint(lim\a,a), listput(v,a*b^a))); Set(v) \\ _Charles R Greathouse IV_, Feb 19 2017
%Y A171607 Cf. A171606. Union of the "KN^K" sequences A001105, A117642, A141046, ... or of the "NK^N" sequences A036289, A036290, A018215, A036291, ... but omitting the trivial initial terms.
%K A171607 nonn
%O A171607 1,1
%A A171607 _Robert Munafo_, Dec 12 2009