A252757 Permutation of natural numbers: a(1)=1, and for n>1, if n is k-th number whose largest prime factor is less than the square of its smallest prime factor [i.e., n = A251726(k)], a(n) = 2*a(k), otherwise, when n = A251727(k), a(n) = 1 + 2*a(k).

1, 2, 4, 8, 16, 32, 64, 128, 256, 3, 512, 6, 1024, 5, 12, 2048, 10, 24, 4096, 9, 20, 17, 48, 8192, 18, 33, 40, 65, 34, 129, 96, 16384, 257, 513, 36, 66, 80, 7, 1025, 13, 130, 2049, 68, 11, 258, 25, 192, 32768, 514, 4097, 21, 49, 1026, 72, 132, 8193, 19, 41, 160, 35, 14, 97, 2050, 26, 260, 16385, 4098, 37, 67, 81, 136, 22

Offset

1,2

Links

Antti Karttunen, Table of n, a(n) for n = 1..10000

Index entries for sequences that are permutations of the natural numbers

Formula

a(1)=1, and for n>1: if A252372(n) = 1 [i.e. the largest prime factor of n is less than the square of its smallest prime factor], a(n) = 2*a(A252373(k)), otherwise, a(n) = 1 + 2*a(n-A252373(n)-1).

Prog

(Scheme, with memoization-macro definec)
(definec (A252757 n) (cond ((<= n 1) n) ((= 1 (A252372 n)) (* 2 (A252757 (A252373 n)))) (else (+ 1 (* 2 (A252757 (- n (A252373 n) 1)))))))

Crossrefs

Inverse: A252758.

Similar permutations: A243287, A135141, A237427.

Cf. A252372, A252373, A251726, A251727.

Sequence in context: A251760 A243086 A087079 * A230579 A361937 A009694

Adjacent sequences: A252754 A252755 A252756 * A252758 A252759 A252760

Keyword

nonn

Author

Antti Karttunen, Jan 02 2015

Status

approved