A158928 a(n) is the smallest integer not yet in the sequence with no common base-3 digit with a(n-1).

1, 2, 3, 8, 4, 6, 13, 18, 40, 20, 121, 24, 364, 26, 9, 80, 10, 242, 12, 728, 27, 2186, 28, 6560, 30, 19682, 31, 59048, 36, 177146, 37, 531440, 39, 1594322, 81, 4782968, 82, 14348906, 84, 43046720, 85, 129140162, 90, 387420488, 91, 1162261466, 93

Offset

1,2

Comments

Numbers of A031944 do not appear in this sequence. After a number which has base-3 digits 0 and 1, a number of the form 3^k-1 (see A024023) follows by definition, because its base-3 digits are all 2.

Links

Table of n, a(n) for n=1..47.

Example

The 4th term cannot be 4 because 4(base10)=11(base3) shares a common digit 1 with a(3)=3(base10)=10(base3). It cannot be 5(base10)=12(base3) because this shares the digit 1 with 3=10(base3). It cannot be 6(base10)=20(base3) because this shares the digit 0 with 3=10(base3). It cannot be 7(base10)=21(base3) because this shares the digit 1 with 3=10(base3). It becomes a(4)=8(base10)=22(base3) which does not have the digit 0 or 1 of a(3)=10(base3).

Crossrefs

Cf. A067581 (base-10), A158929 (base-4), A158930 (base-5).

Sequence in context: A111809 A100869 A110142 * A198369 A193731 A193975

Adjacent sequences: A158925 A158926 A158927 * A158929 A158930 A158931

Keyword

base,easy,nonn

Author

R. J. Mathar, Mar 31 2009

Status

approved