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A128218 First differences of A128217. 4
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 (list; graph; refs; listen; history; text; internal format)
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: A091088 A249781 A115627 * A010283 A134699 A272880

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

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Last modified August 26 03:34 EDT 2019. Contains 326324 sequences. (Running on oeis4.)