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 A260421 a(1) = 1, a(A206074(n)) = 1 + (2*a(n)), a(A205783(1+n)) = 2*a(n), where A206074 and A205783 give binary codes for polynomials with coefficients 0 or 1 that are irreducible [resp. reducible] over Q. 6
 1, 3, 7, 2, 15, 6, 5, 14, 4, 30, 31, 12, 13, 10, 28, 8, 11, 60, 29, 62, 24, 26, 9, 20, 61, 56, 16, 22, 63, 120, 25, 58, 124, 48, 52, 18, 27, 40, 122, 112, 21, 32, 57, 44, 126, 240, 17, 50, 116, 248, 96, 104, 23, 36, 121, 54, 80, 244, 59, 224, 125, 42, 64, 114, 88, 252, 49, 480, 53, 34, 19, 100, 41, 232, 496, 192, 123, 208, 113, 46, 33, 72, 45 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Antti Karttunen, Table of n, a(n) for n = 1..8192 FORMULA If A257000(n) = 1 [when n is one of the terms of A206074] then a(n) = 1 + 2*a(A255574(n)), otherwise a(n) = 2*A260421(A255572(n)). As a composition of related permutations: a(n) = A246377(A260424(n)). a(n) = A246201(A260426(n)). PROG (PARI) allocatemem(123456789); uplim = 2^20; v255574 = vector(uplim); A255574 = n -> v255574[n]; A255572 = n -> (n - A255574(n) - 1); isA206074(n) = polisirreducible(Pol(binary(n))); v255574[1] = 0; i=0; j=0; n=2; while((n < uplim), v255574[n] = v255574[n-1]+isA206074(n); n++); A260421(n) = if(1==n, 1, if(isA206074(n), 1 + 2*(A260421(A255574(n))), 2*(A260421(A255572(n))))); for(n=1, 8192, write("b260421.txt", n, " ", A260421(n))); CROSSREFS Inverse: A260422. Related permutations: A246201, A246377, A260424, A260426. Cf. A257000, A255572, A255574. Sequence in context: A255565 A227351 A246377 * A237427 A210203 A318467 Adjacent sequences:  A260418 A260419 A260420 * A260422 A260423 A260424 KEYWORD nonn AUTHOR Antti Karttunen, Jul 25 2015 STATUS approved

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Last modified May 26 14:46 EDT 2020. Contains 334626 sequences. (Running on oeis4.)