A257506 Inverse permutation to A257505.

1, 3, 6, 2, 10, 15, 21, 28, 36, 45, 55, 5, 66, 78, 91, 9, 105, 4, 120, 136, 153, 14, 171, 190, 210, 231, 253, 276, 300, 325, 351, 378, 406, 435, 465, 496, 528, 561, 595, 630, 666, 703, 741, 780, 820, 861, 903, 20, 946, 990, 1035, 27, 1081, 1128, 1176, 1225, 1275, 1326, 1378, 35, 1431, 1485, 1540, 44, 1596, 54, 1653, 1711, 1770, 65, 1830, 8

Offset: 1

Author

Antti Karttunen, May 06 2015

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..5050
• Index entries for sequences related to factorial base representation
• Index entries for sequences that are permutations of the natural numbers

Crossrefs

Inverse: A257505.

Cf. A257679, A257681.

Programs

Scheme

(define (A257506 n) (let ((row (A257681 n)) (col (A257679 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 r = A257681(n), and c = A257679(n).