

A106446


Doublyrecursed crossdomain bijection from N to GF(2)[X]. Variant of A091204 and A106444.


6



0, 1, 2, 3, 4, 7, 6, 11, 8, 5, 14, 25, 12, 19, 22, 9, 16, 47, 10, 31, 28, 29, 50, 13, 24, 21, 38, 15, 44, 61, 18, 137, 128, 43, 94, 49, 20, 55, 62, 53, 56, 97, 58, 115, 100, 27, 26, 37, 48, 69, 42, 113, 76, 73, 30, 79, 88, 33, 122, 319, 36, 41, 274, 39, 64, 121, 86, 185
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OFFSET

0,3


COMMENTS

Differs from A091204 for the first time at n=32, where A091204(32)=32, while a(32)=128. Differs from A106444 for the first time at n=11, where A106444(11)=13, while a(11)=25.


LINKS

Table of n, a(n) for n=0..67.
A. Karttunen, Schemeprogram for computing this sequence.
Index entries for sequences that are permutations of the natural numbers


FORMULA

a(0)=0, a(1)=1, a(p_i) = A014580(a(i)) for primes p_i with index i and for composites n = p_i^e_i * p_j^e_j * p_k^e_k * ..., a(n) = A048723(a(p_i), a(e_i)) X A048723(a(p_j), a(e_j)) X A048723(a(p_k), a(e_k)) X ..., where X stands for carryless multiplication of GF(2)[X] polynomials (A048720) and A048723(n, y) raises the nth GF(2)[X] polynomial to the y:th power.


EXAMPLE

a(5) = 7, as 5 is the 3rd prime, a(3)=3 and the third irreducible GF(2)[X] polynomial x^2+x+1 is encoded as A014580(3) = 7. a(11) = 25, as 11 is the 5th prime, a(5)=7 and the seventh irreducible GF(2)[X] polynomial x^4+x^3+1 is encoded as A014580(7) = 25. a(32) = a(2^5) = A048723(a(2),a(5)) = A048723(2,7) = 128.


CROSSREFS

Inverse: A106447. Variant: A091204.
Sequence in context: A106444 A106442 A091204 * A321220 A036467 A006875
Adjacent sequences: A106443 A106444 A106445 * A106447 A106448 A106449


KEYWORD

nonn


AUTHOR

Antti Karttunen, May 09 2005


STATUS

approved



