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A255556
Inverse permutation to A255555.
4
1, 3, 2, 5, 6, 10, 4, 8, 15, 9, 14, 21, 28, 36, 7, 12, 45, 20, 13, 55, 66, 19, 27, 78, 35, 44, 91, 105, 120, 136, 11, 17, 153, 54, 26, 171, 190, 18, 65, 210, 77, 25, 231, 253, 276, 34, 90, 300, 43, 53, 325, 351, 104, 119, 378, 135, 152, 406, 435, 465, 496, 528, 16, 23, 561, 170, 64, 595, 630, 33, 189, 666, 209, 24
OFFSET
1,2
FORMULA
a(n) = (1/2) * ((c+r)^2 - r - 3*c + 2), where c = A255559(n), and r = A255560(n).
PROG
(Scheme) (define (A255556 n) (let ((col (A255559 n)) (row (A255560 n))) (* (/ 1 2) (- (expt (+ row col) 2) row col col col -2))))
CROSSREFS
Inverse permutation: A255555.
Sequence in context: A194072 A194105 A194012 * A331462 A308410 A286111
KEYWORD
nonn
AUTHOR
Antti Karttunen, Apr 14 2015
STATUS
approved