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A061579 Reverse one number (0), then two numbers (2,1), then three (5,4,3), then four (9,8,7,6), etc. 14
0, 2, 1, 5, 4, 3, 9, 8, 7, 6, 14, 13, 12, 11, 10, 20, 19, 18, 17, 16, 15, 27, 26, 25, 24, 23, 22, 21, 35, 34, 33, 32, 31, 30, 29, 28, 44, 43, 42, 41, 40, 39, 38, 37, 36, 54, 53, 52, 51, 50, 49, 48, 47, 46, 45, 65, 64, 63, 62, 61, 60, 59, 58, 57, 56, 55, 77, 76, 75, 74, 73, 72 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

a(n) is the smallest nonnegative integer not yet in the sequence such that n + a(n) is one less than a square. [From Franklin T. Adams-Watters, Apr 06 2009]

LINKS

Harry J. Smith, Table of n, a(n) for n = 0..1000

Index entries for sequences that are permutations of the natural numbers

FORMULA

a(n) =[sqrt(2n+1)-1/2]*[sqrt(2n+1)+3/2]-n =A005563(A003056(n))-n

MATHEMATICA

Module[{nn=20}, Reverse/@TakeList[Range[0, (nn(nn+1))/2], Range[nn]]]// Flatten (* Requires Mathematica version 11 or later *) (* Harvey P. Dale, Jul 06 2018 *)

PROG

(PARI) default(realprecision, 100); for (n=0, 1000, f=floor(sqrt(2*n + 1) - 1/2); write("b061579.txt", n, " ", f*(f + 2) - n) ) \\ Harry J. Smith, Jul 25 2009

CROSSREFS

Fixed points are A046092. Each reversal involves the numbers from A000217 through to A000096.

A self-inverse permutation of the nonnegative numbers.

Cf. A038722. Transpose of A001477.

Sequence in context: A275131 A280513 A185023 * A094064 A159930 A058344

Adjacent sequences:  A061576 A061577 A061578 * A061580 A061581 A061582

KEYWORD

nonn,tabl

AUTHOR

Henry Bottomley, May 21 2001

STATUS

approved

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Last modified March 31 22:16 EDT 2020. Contains 333151 sequences. (Running on oeis4.)