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A278504
Inverse permutation to A278503.
4
1, 3, 2, 6, 5, 10, 4, 15, 8, 21, 9, 28, 7, 36, 12, 45, 14, 55, 11, 66, 13, 78, 20, 91, 17, 105, 16, 120, 27, 136, 23, 153, 19, 171, 35, 190, 18, 210, 22, 231, 44, 253, 30, 276, 26, 300, 54, 325, 29, 351, 24, 378, 65, 406, 25, 435, 34, 465, 77, 496, 38, 528, 37, 561, 90, 595, 47, 630, 43, 666, 104, 703, 31, 741, 33, 780, 119, 820, 46
OFFSET
1,2
FORMULA
a(n) = (1/2) * ((c+r)^2 - r - 3*c + 2), where c = A278538(n), and r = A278539(n).
PROG
(Scheme) (define (A278504 n) (let ((row (A278539 n)) (col (A278538 n))) (* (/ 1 2) (- (expt (+ row col) 2) row col col col -2))))
CROSSREFS
Inverse: A278503.
Cf. also A278506, A278512.
Sequence in context: A069159 A306389 A255548 * A085179 A113782 A090868
KEYWORD
nonn
AUTHOR
Antti Karttunen, Nov 23 2016
STATUS
approved