A277881 Inverse permutation to A277880.

1, 3, 2, 6, 5, 4, 10, 15, 9, 8, 21, 7, 28, 36, 14, 45, 20, 13, 55, 12, 66, 78, 27, 11, 91, 105, 35, 120, 44, 19, 136, 153, 54, 26, 171, 18, 190, 210, 65, 17, 231, 253, 77, 276, 90, 34, 300, 16, 325, 351, 104, 378, 119, 43, 406, 435, 135, 53, 465, 25, 496, 528, 152, 561, 170, 64, 595, 33, 630, 666, 189, 24, 703, 741, 209, 780, 230, 76, 820, 23

Offset: 1

Author

Antti Karttunen, Nov 03 2016

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..16384
• Index entries for sequences that are permutations of the natural numbers

Crossrefs

Inverse: A277880.

Cf. A277813, A277822.

Cf. A028401 (terms at powers of 2).

Programs

Scheme

(define (A277881 n) (let ((row (A277813 n)) (col (A277822 n))) (* (/ 1 2) (- (expt (+ row col) 2) row col col col -2))))

Formula

a(n) = (1/2) * ((c+r)^2 - r - 3*c + 2), where c = A277822(n), and r = A277813(n).