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 A257506 Inverse permutation to A257505. 3
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Antti Karttunen, Table of n, a(n) for n = 1..5050 FORMULA a(n) = (1/2) * ((c+r)^2 - r - 3*c + 2), where r = A257681(n), and c = A257679(n). PROG (Scheme) (define (A257506 n) (let ((row (A257681 n)) (col (A257679 n))) (* (/ 1 2) (- (expt (+ row col) 2) row col col col -2)))) CROSSREFS Inverse: A257505. Cf. A257679, A257681. Sequence in context: A257106 A210187 A210189 * A210035 A210199 A268717 Adjacent sequences:  A257503 A257504 A257505 * A257507 A257508 A257509 KEYWORD nonn AUTHOR Antti Karttunen, May 06 2015 STATUS approved

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Last modified November 30 10:52 EST 2021. Contains 349419 sequences. (Running on oeis4.)