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A030690 Smallest nontrivial extension of n-th square which is a cube.

%I A030690 #8 May 24 2016 23:53:19
%S A030690 125,4096,9261,166375,250047,3652264,4913,64000,8120601,1000,12167,
%T A030690 1442897,16974593,19683,225866529,25672375,28934443,3241792,
%U A030690 3616805375,40001688,4410944,4843965888,529475129,5764224257
%N A030690 Smallest nontrivial extension of n-th square which is a cube.
%H A030690 Chai Wah Wu, <a href="/A030690/b030690.txt">Table of n, a(n) for n = 1..10000</a>
%o A030690 (Python)
%o A030690 from gmpy2 import iroot
%o A030690 def A030690(n):
%o A030690     d, nd = 10, 10*n**2
%o A030690     while True:
%o A030690         x = (iroot(nd-1,3)[0]+1)**3
%o A030690         if x < nd+d:
%o A030690             return int(x)
%o A030690         d *= 10
%o A030690         nd *= 10 # _Chai Wah Wu_, May 24 2016
%Y A030690 Cf. A030691.
%K A030690 nonn,base
%O A030690 1,1
%A A030690 _Patrick De Geest_