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 A292253 a(1) = 0, a(2) = 1, and for n > 2, a(n) = 2*a(A252463(n)) + [n == 1 (mod 2)]*[J(3|n) == 1], where J is the Jacobi-symbol. 8
 0, 1, 2, 2, 4, 4, 8, 4, 4, 8, 17, 8, 35, 16, 8, 8, 70, 8, 140, 16, 16, 34, 281, 16, 9, 70, 8, 32, 562, 16, 1124, 16, 32, 140, 17, 16, 2249, 280, 68, 32, 4498, 32, 8996, 68, 16, 562, 17993, 32, 19, 18, 140, 140, 35986, 16, 32, 64, 280, 1124, 71973, 32, 143947, 2248, 32, 32, 64, 64, 287894, 280, 560, 34, 575789, 32, 1151579, 4498, 16, 560, 34, 136, 2303158, 64 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Base-2 expansion of a(n) encodes the steps where numbers that are either of the form 12k+1 or of the form 12k+11 are encountered when map x -> A252463(x) is iterated down to 1, starting from x=n. An exception is the most significant bit of a(n) which corresponds with the final 1, but is shifted one bit-position towards right. The AND - XOR formula(s) just restate the fact that J(3|n) = J(-1|n)*J(-3|n), as the Jacobi-symbol is multiplicative (also) with respect to its upper argument. LINKS Antti Karttunen, Table of n, a(n) for n = 1..2048 FORMULA a(1) = 0, a(2) = 1, and for n > 2, a(n) = 2*a(A252463(n)) + [n == 1 (mod 2)]*[J(3|n) == 1], where J is the Jacobi-symbol, and [ ]'s are Iverson brackets, whose product gives 1 only if n is an odd number for which J(3|n) = +1, and 0 otherwise. a(n) = A292263(n) AND (A292383(n) XOR A292941(n)), where AND is bitwise-and (A004198) and XOR is bitwise-XOR (A003987). [See comments.] For n >= 0, a(A163511(n)) = A292254(n). For n >= 1, a(n) + A292255(n) + A292943(n) = A243071(n). PROG (Scheme) (define (A292253 n) (if (<= n 2) (- n 1) (+ (if (and (odd? n) (= 1 (jacobi-symbol 3 n))) 1 0) (* 2 (A292253 (A252463 n)))))) CROSSREFS Cf. A005940, A163511, A243071, A292254, A292255, A292263, A292941, A292943, A292383. Sequence in context: A222737 A005852 A274625 * A115209 A139210 A300123 Adjacent sequences:  A292250 A292251 A292252 * A292254 A292255 A292256 KEYWORD nonn AUTHOR Antti Karttunen, Sep 28 2017 STATUS approved

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Last modified February 23 11:52 EST 2020. Contains 332159 sequences. (Running on oeis4.)