A256996 Inverse to A256995 considered as a permutation of natural numbers, with assumed fixed initial term a(1) = 1.

1, 2, 3, 5, 4, 7, 8, 6, 11, 10, 12, 16, 22, 29, 9, 15, 37, 14, 17, 46, 56, 21, 28, 67, 36, 13, 79, 92, 106, 121, 20, 45, 137, 19, 23, 154, 172, 55, 66, 191, 27, 35, 211, 232, 254, 78, 44, 277, 18, 91, 301, 326, 105, 120, 352, 136, 26, 379, 407, 436, 466, 497, 54, 153, 529, 25, 30, 562, 596, 171, 190, 631, 65, 77, 667, 704, 742, 210, 34, 781, 43

Offset: 1

Author

Antti Karttunen, Apr 14 2015

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..10000
• Index entries for sequences that are permutations of the natural numbers

Crossrefs

Inverse: A256995.

Cf. A256989, A256990.

Cf. also A256998, A255556.

Programs

Scheme

(define (A256996 n) (if (= 1 n) n (let ((col (A256989 n)) (row (A256990 n))) (+ 1 (* (/ 1 2) (- (expt (+ row col) 2) row col col col -2))))))

Formula

a(1) = 1, and for n > 1: a(n) = (1/2) * ((c+r)^2 - r - 3*c + 4), where c = A256989(n), and r = A256990(n).