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 A054425 A054424 expanded to normal triangular array, with zeros at those (x,y) where x and y are not relatively prime. 9
 1, 2, 3, 4, 0, 7, 8, 5, 6, 15, 16, 0, 0, 0, 31, 32, 9, 11, 12, 14, 63, 64, 0, 10, 0, 13, 0, 127, 128, 17, 0, 23, 24, 0, 30, 255, 256, 0, 19, 0, 0, 0, 28, 0, 511, 512, 33, 18, 20, 47, 48, 27, 29, 62, 1023, 1024, 0, 0, 0, 22, 0, 25, 0, 0, 0, 2047, 2048, 65, 35, 39, 21, 95, 96, 26, 56 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Cf. A054431 LINKS FORMULA a(n) = A054424_as_array(n) MAPLE position_in_whole_SB_tree_or_zero := (n, m) -> `if`((1 = gcd(n, m)), (frac2position_in_whole_SB_tree(n/m)), (0)); A054424_as_array := n -> position_in_whole_SB_tree_or_zero( ((n-((trinv(n)*(trinv(n)-1))/2))+1), ((((trinv(n)-1)*(((1/2)*trinv(n))+1))-n)+1) ); trinv := n -> floor((1+sqrt(1+8*n))/2); # Gives integral inverses to the triangular numbers CROSSREFS Sequence in context: A004180 A011418 A214158 * A217101 A265516 A256295 Adjacent sequences:  A054422 A054423 A054424 * A054426 A054427 A054428 KEYWORD nonn,tabl,nice AUTHOR STATUS approved

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Last modified December 13 06:26 EST 2019. Contains 329968 sequences. (Running on oeis4.)