A349681 a(1)=1, a(2)=2; for n > 2, a(n) is the least unused positive number k such that j != k and either j | k or k | j, but not both, where j = a(n-1) + 1.

1, 2, 6, 14, 3, 8, 18, 38, 13, 7, 4, 10, 22, 46, 94, 5, 12, 26, 9, 20, 42, 86, 29, 15, 32, 11, 24, 50, 17, 36, 74, 25, 52, 106, 214, 43, 88, 178, 358, 718, 1438, 2878, 5758, 443, 37, 19, 40, 82, 166, 334, 67, 34, 70, 142, 286, 41, 21, 44, 90, 182, 61, 31, 16, 51

Offset

1,2

Comments

Variant of A347113 with the additional restriction that j | k or k | j. - Michael De Vlieger, Dec 18 2021.

Links

Michael De Vlieger, Table of n, a(n) for n = 1..10000

Michael De Vlieger, Log-log scatterplot of a(n), for n = 1..2^14, indicating records in red and local minima in blue.

Mathematica

j = 3; c[_] = 0; c[2] = 1; {1, 2}~Join~Reap[Do[Set[k, 3]; While[Nand[c[k] == 0, j != k, Xor[Mod[j, k] == 0, Mod[k, j] == 0]], k++]; Sow[k]; Set[c[k], i]; j = k + 1, {i, 3, 64}]][[-1, -1]]

Crossrefs

Cf. A347113.

Sequence in context: A012470 A266960 A056592 * A282544 A091719 A058054

Adjacent sequences: A349678 A349679 A349680 * A349682 A349683 A349684

Keyword

nonn

Author

Michael De Vlieger, Nov 25 2021

Status

approved