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A109857
Next 2*n - 1 odd numbers in decreasing order followed by next 2*n even numbers in decreasing order.
1
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
1,2
COMMENTS
This sequence is a permutation of the positive integers. - 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)
EXAMPLE
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;
PROG
(PARI) T(n, k)=n*(n+1)/2+floor(n/2)-2*(k-1) \\ Werner Schulte, Jul 29 2023
CROSSREFS
Cf. A074147 (row reversed), A074149 (row sums), A074148 (column 1), A001844, A061925 (main diagonal).
Sequence in context: A021963 A131914 A115302 * A194075 A271479 A259927
KEYWORD
easy,nonn,tabl
AUTHOR
Amarnath Murthy, Jul 08 2005
EXTENSIONS
More terms from Joshua Zucker, May 05 2006
STATUS
approved