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A004976
a(n) = floor(n*phi^3), where phi=(1+sqrt(5))/2.
33
0, 4, 8, 12, 16, 21, 25, 29, 33, 38, 42, 46, 50, 55, 59, 63, 67, 72, 76, 80, 84, 88, 93, 97, 101, 105, 110, 114, 118, 122, 127, 131, 135, 139, 144, 148, 152, 156, 160, 165, 169, 173, 177, 182, 186, 190, 194, 199
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OFFSET
0,2
COMMENTS
For n>=1, a(n) is the position of the n-th 1 in the zero-one sequence [n*r+r]-[n*r]-[r], where r=sqrt(5); see
A188221
. Also,
A004976
=-1+
A004958
(for n>=1), and
A004976
is the complement of
A188222
. -
Clark Kimberling
, Mar 24 2011
LINKS
Vincenzo Librandi,
Table of n, a(n) for n = 0..1000
A. J. Hildebrand, Junxian Li, Xiaomin Li, and Yun Xie,
Almost Beatty Partitions
, arXiv:1809.08690 [math.NT], 2018.
Vincent Russo and Loren Schwiebert,
Beatty Sequences, Fibonacci Numbers, and the Golden Ratio
, The Fibonacci Quarterly, Vol 49, Number 2, May 2011.
Index entries for sequences related to Beatty sequences
FORMULA
a(n) = n+floor(2*n*phi). [Formula corrected by
Clark Kimberling
, Mar 22 2008]
MATHEMATICA
r=5^(1/2); k=1;
t=Table[Floor[n*r+k*r]-Floor[n*r]-Floor[k*r], {n, 1, 220}] (*
A188221
*)
Flatten[Position[t, 0] ] (*
A188222
*)
Flatten[Position[t, 1] ] (*
A004976
*)
(*
Clark Kimberling
, Mar 24 2011 *)
With[{c=GoldenRatio^3}, Floor[c*Range[0, 50]]] (*
Vincenzo Librandi
, Apr 12 2012 *)
PROG
(PARI) a(n)=2*n+sqrtint(5*n^2) \\
Charles R Greathouse IV
, Apr 12 2012
(Python)
from math import isqrt
def
A004976
(n): return (isqrt(20*n**2)>>1)+(n<<1) #
Chai Wah Wu
, Aug 17 2022
CROSSREFS
Cf.
A000201
,
A001950
,
A004919
,
A004958
,
A188221
,
A188222
.
Sequence in context:
A311254
A311255
A190885
*
A341254
A311256
A311257
Adjacent sequences:
A004973
A004974
A004975
*
A004977
A004978
A004979
KEYWORD
nonn
,
easy
AUTHOR
N. J. A. Sloane
STATUS
approved