OFFSET
0,3
COMMENTS
Complement of A158582. - Reinhard Zumkeller, Apr 16 2009
Numbers of the form 2^t - 2^k - 1, 0 <= k < t.
n is in the sequence if and only if 2*n+1 is in the sequence. - Robert Israel, Dec 14 2018
Also the least binary rank of a strict integer partition of n, where the binary rank of a partition y is given by Sum_i 2^(y_i-1). - Gus Wiseman, May 24 2024
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 0..10000
Vladimir Shevelev, On the Basis Polynomials in the Theory of Permutations with Prescribed Up-Down Structure, arXiv:0801.0072 [math.CO], 2007-201. See Section 14.
Vladimir Shevelev, Binomial Coefficient Predictors, Journal of Integer Sequences, Vol. 14 (2011), Article 11.2.8.
Vladimir Shevelev, The number of permutations with prescribed up-down structure as a function of two variables, INTEGERS, 12 (2012), #A1.
FORMULA
a(0)=0, n>0: a(n+1) = Min{m>n: BinOnes(a(n))<=BinOnes(m)} with BinOnes=A000120.
If m = floor((sqrt(8*n+1) - 1) / 2), then a(n) = 2^(m+1) - 2^(m*(m+3)/2 - n) - 1. - Carl R. White, Feb 10 2009
a(A014132(n)-1) = 2*a(n-1)+1 for n >= 1. - Robert Israel, Dec 14 2018
EXAMPLE
From Tilman Piesk, May 09 2012: (Start)
This may also be viewed as a triangle: In binary:
0 0
1 2 01 10
3 5 6 011 101 110
7 11 13 14 0111 1011 1101 1110
15 23 27 29 30 01111 10111 11011 11101 11110
31 47 55 59 61 62
63 95 111 119 123 125 126
Left three diagonals are A000225, A055010, A086224. Right diagonal is A000918. Central column is A129868. Numbers in row n (counted from 0) have n binary 1s. (End)
From Gus Wiseman, May 24 2024: (Start)
The terms together with their binary expansions and binary indices begin:
0: 0 ~ {}
1: 1 ~ {1}
2: 10 ~ {2}
3: 11 ~ {1,2}
5: 101 ~ {1,3}
6: 110 ~ {2,3}
7: 111 ~ {1,2,3}
11: 1011 ~ {1,2,4}
13: 1101 ~ {1,3,4}
14: 1110 ~ {2,3,4}
15: 1111 ~ {1,2,3,4}
23: 10111 ~ {1,2,3,5}
27: 11011 ~ {1,2,4,5}
29: 11101 ~ {1,3,4,5}
30: 11110 ~ {2,3,4,5}
31: 11111 ~ {1,2,3,4,5}
47: 101111 ~ {1,2,3,4,6}
55: 110111 ~ {1,2,3,5,6}
59: 111011 ~ {1,2,4,5,6}
61: 111101 ~ {1,3,4,5,6}
62: 111110 ~ {2,3,4,5,6}
(End)
MAPLE
seq(seq(2^a-1-2^b, b=a-1..0, -1), a=1..11); # Robert Israel, Dec 14 2018
MATHEMATICA
fQ[n_] := DigitCount[n, 2, 0] < 2; Select[ Range[0, 2^10], fQ] (* Robert G. Wilson v, Aug 02 2012 *)
PROG
(Haskell)
a089633 n = a089633_list !! (n-1)
a089633_list = [2 ^ t - 2 ^ k - 1 | t <- [1..], k <- [t-1, t-2..0]]
-- Reinhard Zumkeller, Feb 23 2012
(PARI) {insq(n) = local(dd, hf, v); v=binary(n); hf=length(v); dd=sum(i=1, hf, v[i]); if(dd<=hf-2, -1, 1)}
{for(w=0, 1536, if(insq(w)>=0, print1(w, ", ")))}
\\ Douglas Latimer, May 07 2013
(PARI) isoka(n) = #select(x->(x==0), binary(n)) <= 1; \\ Michel Marcus, Dec 14 2018
(Python)
from itertools import count, islice
def A089633_gen(): # generator of terms
return ((1<<t)-(1<<k)-1 for t in count(1) for k in range(t-1, -1, -1))
(Python)
from math import isqrt, comb
def A089633(n): return (1<<(a:=(isqrt((n<<3)+1)-1>>1)+1))-(1<<comb(a, 2)+a-1-n)-1 # Chai Wah Wu, Dec 19 2024
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Reinhard Zumkeller, Jan 01 2004
STATUS
approved