A064790 Inverse permutation to A060734.
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
Offset: 1
Examples
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)
Links
- Boris Putievskiy, Transformations Integer Sequences And Pairing Functions, arXiv:1212.2732 [math.CO], 2012.
- Eric Weisstein's MathWorld, Pairing Function
- Index entries for sequences that are permutations of the natural numbers
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
Comments