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 A260739 Column index to A255127: a(1) = 1; for n > 1, a(n) = the position at the stage where n is removed in the sieve which produces Ludic numbers. 17
 1, 1, 1, 2, 1, 3, 1, 4, 2, 5, 1, 6, 1, 7, 3, 8, 1, 9, 2, 10, 4, 11, 1, 12, 1, 13, 5, 14, 1, 15, 2, 16, 6, 17, 3, 18, 1, 19, 7, 20, 1, 21, 1, 22, 8, 23, 1, 24, 4, 25, 9, 26, 1, 27, 2, 28, 10, 29, 3, 30, 1, 31, 11, 32, 5, 33, 1, 34, 12, 35, 1, 36, 2, 37, 13, 38, 1, 39, 6, 40, 14, 41, 1, 42, 4, 43, 15, 44, 1, 45, 1, 46, 16, 47, 7, 48, 1, 49, 17, 50, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS Ordinal transform of A272565 (Ludic factor), and also of A260738. - Antti Karttunen, Apr 03 2018 LINKS Antti Karttunen, Table of n, a(n) for n = 1..10105 FORMULA Other identities. For all n >= 2: a(A003309(n)) = 1. [In Ludic sieve each Ludic number (after 1) is the first among the numbers removed at stage k.] a(A254100(n)) = 2. A255127(A260738(n), a(n)) = n. For n > 1, A001511(a(n)) = A302035(n). - Antti Karttunen, Apr 03 2018 PROG (Scheme) (define (A260739 n) (cond ((= 1 n) 1) ((even? n) (/ n 2)) (else (let searchrow ((row 2)) (let searchcol ((col 1)) (cond ((>= (A255127bi row col) n) (if (= (A255127bi row col) n) col (searchrow (+ 1 row)))) (else (searchcol (+ 1 col))))))))) ;; Code for A255127bi given in A255127. CROSSREFS Column index to array A255127. Cf. A003309, A254100, A272565. Cf. A260738 (corresponding row index). Cf. A302035, A302036 (positions of terms that are powers of 2). Cf. A078898, A246277, A260429, A260439 for column indices to other arrays similar to A255127. Differs from A246277 (and also after the initial term from A078898) for the first time at n=19. Sequence in context: A305438 A078898 A246277 * A130747 A055440 A250028 Adjacent sequences:  A260736 A260737 A260738 * A260740 A260741 A260742 KEYWORD nonn AUTHOR Antti Karttunen, Jul 30 2015 EXTENSIONS Term a(1) changed from 0 to 1 to match with the definition of A078898 and the interpretation as an ordinal transform - Antti Karttunen, Apr 03 2018 STATUS approved

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Last modified July 26 02:06 EDT 2021. Contains 346294 sequences. (Running on oeis4.)