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A064790 Inverse permutation to A060734. 4
1, 3, 5, 2, 6, 9, 13, 8, 4, 10, 14, 19, 25, 18, 12, 7, 15, 20, 26, 33, 41, 32, 24, 17, 11, 21, 27, 34, 42, 51, 61, 50, 40, 31, 23, 16, 28, 35, 43, 52, 62, 73, 85, 72, 60, 49, 39, 30, 22, 36, 44, 53, 63, 74, 86, 99, 113, 98, 84, 71, 59, 48, 38, 29, 45, 54, 64, 75, 87, 100, 114 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

From Boris Putievskiy, Mar 14 2013: (Start)

a(n) is a pairing function: a function that reversibly maps Z^{+} x Z^{+} onto Z^{+}, where Z^{+} is the set of integer positive numbers.

Layer is pair of sides of square from T(1,n) to T(n,n) and  from T(n,n) to T(n,1). This sequence is A188568 as table read  by boustrophedonic ("ox-plowing") method - layer clockwise, layer counterclockwise and so. The same table A188568 read layer by layer clockwise is A194280. (End)

LINKS

Table of n, a(n) for n=1..71.

Index entries for sequences that are permutations of the natural numbers

Boris Putievskiy, Transformations Integer Sequences And Pairing Functions arXiv:1212.2732 [math.CO]

Eric Weisstein's MathWorld, Pairing Function

FORMULA

a(n) = (i+j-1)*(i+j-2)/2+i, where i=min(t; t^2-n+1), j=min(t; n-(t-1)^2), t=floor(sqrt(n-1))+1. - Boris Putievskiy, Dec 24 2012

EXAMPLE

From Boris Putievskiy, Mar 14 2013: (Start)

The start of the sequence as table:

1....2...6...7..15..16..28...

3....5...9..12..20..23..35...

4....8..13..18..26..31..43...

10..14..19..25..33..40..52...

11..17..24..32..41..50..62...

21..27..34..42..51..61..73...

22..30..39..49..60..72..85...

. . .

The start of the sequence as triangular array read by rows:

1;

3,5,2;

6,9,13,8,4;

10,14,19,25,18,12,7;

15,20,26,33,41,32,24,17,11;

21,27,34,42,51,61,50,40,31,23,16;

28,35,43,52,62,73,85,72,60,49,39,30,22;

. . .

Row number r contains 2*r-1 numbers. (End)

CROSSREFS

Cf. A060734, A064788, A188568, A194280.

Sequence in context: A302793 A010782 A139584 * A113966 A164611 A316086

Adjacent sequences:  A064787 A064788 A064789 * A064791 A064792 A064793

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Oct 20 2001

STATUS

approved

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Last modified January 17 22:51 EST 2019. Contains 319251 sequences. (Running on oeis4.)