A128218 First differences of A128217.

1, 3, 1, 3, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 1, 7, 1, 1, 1, 1, 1, 7, 1, 1, 1, 1, 1, 1, 9, 1, 1, 1, 1, 1, 1, 1, 9, 1, 1, 1, 1, 1, 1, 1, 1, 11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 13, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 13, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 15, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1

Offset

1,2

Comments

a(A130883(n-1)) = 2*n-1 and a(m) != 2*n-1 for m < A130883(n-1). - Reinhard Zumkeller, Jun 20 2015

Links

Table of n, a(n) for n=1..103.

Formula

Let A(1)={1}. Then, for k=2,3,4,..., form A(k) by appending to A(k-1) the term k-1 followed by k-1 1's, if k is even, or by appending to A(k-1) the term k followed by k-1 1's, if k is odd. {a(n)} appears to be the limit of {A(k)} as k->infinity.

Mathematica

nsrQ[n_]:=Module[{sr=Sqrt[n]}, Abs[First[sr-Nearest[{Floor[sr], Ceiling[ sr]}, sr]]]<1/4]; Differences[Select[Range[0, 250], nsrQ]] (* Harvey P. Dale, May 02 2012 *)

Prog

(Haskell)
a128218 n = a128218_list !! (n-1)
a128218_list = zipWith (-) (tail a128217_list) a128217_list
-- Reinhard Zumkeller, Jun 20 2015

Crossrefs

Cf. A128127.

Cf. A130883, A152271 (run lengths after initial term).

Sequence in context: A249781 A342041 A115627 * A010283 A134699 A331286

Adjacent sequences: A128215 A128216 A128217 * A128219 A128220 A128221

Keyword

nonn

Author

John W. Layman, Feb 19 2007

Extensions

Offset changed by Reinhard Zumkeller, Jun 20 2015

Status

approved