A080763 Exchange 1's and 2's in the eta-sequence A006337.

2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 2

Offset

1,1

Links

T. D. Noe, Table of n, a(n) for n=1..10000

N. J. A. Sloane, Families of Essentially Identical Sequences, Mar 24 2021 (Includes this sequence)

Formula

Digits := 100: c2 := sqrt(2.): A080763 := n->3-floor((n+1)*c2)+floor(n*c2);

Mathematica

Flatten[ Table[ Nest[ Flatten[ # /. {1 -> {2, 2, 1}, 2 -> {2, 1}}] &, {2}, n], {n, 5}]] (* Robert G. Wilson v, May 06 2005 *)

Prog

(Python)
from math import isqrt
def A080763(n): return 3+isqrt(m:=n*n<<1)-isqrt(m+(n<<2)+2) # Chai Wah Wu, Aug 03 2022

Crossrefs

Different from A022921.

The following sequences are all essentially the same, in the sense that they are simple transformations of each other, with A003151 as the parent: A003151, A001951, A001952, A003152, A006337, A080763, A082844 (conjectured), A097509, A159684, A188037, A245219 (conjectured), A276862. - N. J. A. Sloane, Mar 09 2021

Sequence in context: A309858 A375508 A022921 * A245920 A165413 A172155

Adjacent sequences: A080760 A080761 A080762 * A080764 A080765 A080766

Keyword

nonn,easy

Author

N. J. A. Sloane, Mar 25 2003

Status

approved