A338942 Lexicographically earliest sequence of distinct positive terms such that a(n) is present in 3*a(n+1).

1, 4, 8, 6, 2, 7, 9, 3, 10, 34, 78, 26, 42, 14, 38, 46, 82, 94, 98, 66, 22, 74, 58, 86, 62, 54, 18, 60, 20, 40, 80, 160, 534, 178, 594, 198, 660, 220, 734, 578, 526, 842, 614, 538, 846, 282, 940, 980, 1660, 5534, 5178, 1726, 5754, 1918, 6394, 8798, 6266, 5422, 8474, 6158, 5386, 8462, 6154, 8718, 2906, 4302, 1434, 478

Offset

1,2

Comments

The lexicographically earliest sequence of positive terms such that a(n) is present in 2*a(n+1) is A000351 (the powers of 5).

Links

Carole Dubois, Table of n, a(n) for n = 1..270

Example

a(1) = 1 is present (as a substring) in 12 [= 3 * a(n+1) = 3 * 4)];
a(2) = 4 is present in 24 (= 3 * 8);
a(3) = 8 is present in 18 (= 3 * 6);
a(4) = 6 is present in 6 (= 3 * 2); etc.

Prog

(Magma) a:=[1]; f:=func<n, m|IntegerToString(n) in IntegerToString(m)>; for n in [2..70] do k:=2; while k in a or not f(a[n-1], 3*k) do k:=k+1; end while; Append(~a, k); end for; a; // Marius A. Burtea, Nov 19 2020

Crossrefs

Cf. A210013, A000351.

Sequence in context: A193082 A348563 A201335 * A219246 A296488 A199294

Adjacent sequences: A338939 A338940 A338941 * A338943 A338944 A338945

Keyword

base,nonn

Author

Eric Angelini and Carole Dubois, Nov 17 2020

Status

approved