A109857 Next 2*n - 1 odd numbers in decreasing order followed by next 2*n even numbers in decreasing order.

1, 4, 2, 7, 5, 3, 12, 10, 8, 6, 17, 15, 13, 11, 9, 24, 22, 20, 18, 16, 14, 31, 29, 27, 25, 23, 21, 19, 40, 38, 36, 34, 32, 30, 28, 26, 49, 47, 45, 43, 41, 39, 37, 35, 33, 60, 58, 56, 54, 52, 50, 48, 46, 44, 42, 71, 69, 67, 65, 63, 61, 59, 57, 55, 53, 51, 84, 82, 80, 78, 76, 74

Offset: 1

Author

Amarnath Murthy, Jul 08 2005

Keywords

• easy
• nonn
• tabl

Comments

This sequence is a permutation of the positive integers. - Werner Schulte, Jul 29 2023

Examples

			 1;
 4,  2;
 7,  5,  3;
12, 10,  8,  6;
17, 15, 13, 11,  9;
24, 22, 20, 18, 16, 14;
31, 29, 27, 25, 23, 21, 19;
40, 38, 36, 34, 32, 30, 28, 26;
		

Crossrefs

Cf. A074147 (row reversed), A074149 (row sums), A074148 (column 1), A001844, A061925 (main diagonal).

Programs

PARI

T(n,k)=n*(n+1)/2+floor(n/2)-2*(k-1) \\ Werner Schulte, Jul 29 2023

Formula

From Werner Schulte, Jul 29 2023: (Start)

T(n, k) = n*(n+1)/2 + floor(n/2) - 2*(k-1) for 1 <= k <= n.

T(n, n) = (n^2-3*n+4)/2 + floor(n/2) for n > 0.

T(2*n-1, n) = n^2 + (n-1)^2 = A001844(n-1) for n > 0. (End)

Extensions

More terms from Joshua Zucker, May 05 2006