A115656 - OEIS

%I #8 Oct 06 2014 21:22:59

%S 1,4,8,9,27,72,100,121,144,169,343,400,441,484,576,675,676,800,900,

%T 961,1000,1089,1331,1800,2700,3087,4000,7200,7803,8000,9000,9801,

%U 10000,10201,10404,10609,12100,12321,12544,12769,14400,14641,14884

%N Both n and the reverse of n are powerful(1) numbers (A001694).

%H Charles R Greathouse IV, <a href="/A115656/b115656.txt">Table of n, a(n) for n = 1..6228</a>

%e 9801=3^4*11^2 and 1089=3^2*11^2.

%o (PARI) is(n)=ispowerful(n) && ispowerful(subst(Polrev(digits(n)),'x,10)) \\ _Charles R Greathouse IV_, Sep 16 2014

%o (PARI) has(n)=ispowerful(subst(Polrev(digits(n)),'x,10))

%o list(lim)=my(v=List(),t,t2); for(m=1,lim^(1/3), t=m^3; for(n=1,sqrtint(lim\t), if(has(t2=t*n^2), listput(v,t2)))); Set(v) \\ _Charles R Greathouse IV_, Sep 16 2014

%Y Cf. A001694, A115655, A085751.

%K base,nonn

%O 1,2

%A _Giovanni Resta_, Jan 28 2006