A017980 - OEIS

%I #14 Jun 18 2024 20:31:27

%S 1,1,2,2,3,3,4,5,6,8,10,13,16,20,25,32,40,51,64,81,102,128,161,203,

%T 256,323,406,512,645,813,1024,1290,1625,2048,2580,3251,4096,5161,6502,

%U 8192,10321,13004,16384,20643,26008,32768,41285,52016,65536,82570,104032

%N Powers of cube root of 2 rounded to nearest integer.

%H Vincenzo Librandi, <a href="/A017980/b017980.txt">Table of n, a(n) for n = 0..200</a>

%t Table[Round[2^(n/3)], {n, 0, 50}] (* _Vincenzo Librandi_, Jan 07 2014 *)

%t Round[Surd[2,3]^Range[0,50]] (* _Harvey P. Dale_, Oct 07 2014 *)

%o (Magma) [Round(2^(n/3)): n in [0..50]]; // _Vincenzo Librandi_, Jan 07 2014

%o (Python)

%o from sympy import integer_nthroot

%o def A017980(n): return -integer_nthroot(m:=1<<n,3)[0]+integer_nthroot(m<<3,3)[0] # _Chai Wah Wu_, Jun 18 2024

%Y Cf. powers of cube root of k rounded up: this sequence (k=2), A017983 (k=3), A017986 (k=4), A017989 (k=5), A017992 (k=6), A017995 (k=7), A018001 (k=9), A018004 (k=10), A018007 (k=11), A018010 (k=12), A018013 (k=13), A018016 (k=14), A018019 (k=15), A018022 (k=16), A018025 (k=17), A018028 (k=18), A018031 (k=19), A018034 (k=20), A018037 (k=21), A018040 (k=22), A018043 (k=23), A018046 (k=24).

%K nonn

%O 0,3

%A _N. J. A. Sloane_.

%E More terms from _Vincenzo Librandi_, Jan 07 2014