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%I #15 Jul 12 2014 11:48:11
%S 0,1,4,8,18,27,48,64,100,125,180,216,294,343,448,512,648,729,900,1000,
%T 1210,1331,1584,1728,2028,2197,2548,2744,3150,3375,3840,4096,4624,
%U 4913,5508,5832,6498,6859,7600,8000,8820,9261,10164,10648,11638,12167,13248
%N Natural numbers k such that floor(v) * ceiling(v)^2 = k, where v = k^(1/3).
%F It appears that a(n) = n^3/8 if n is even, a(n) = (n-1)*(n+1)^2/8 if n is odd.
%F Empirical g.f.: x^2*(x^3+x^2+3*x+1) / ((x-1)^4*(x+1)^3). - _Colin Barker_, Jul 08 2014
%o (PARI) isok(k) = {cbr = sqrtnint(k, 3); if (cbr^3 == k, 1, cbr*(cbr+1)^2 == k);} \\ _Michel Marcus_, Jul 08 2014
%Y Cf. A002620, A006501.
%K nonn
%O 1,3
%A _John W. Layman_, Mar 21 2012