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 A365986 Multiply each term by 3 and erase the leftmost digit of the result: this leaves the sequence unchanged. 2

%I #19 Sep 25 2023 04:49:22

%S 1,7,9,13,71,57,119,373,791,597,1199,3733,7911,12637,70879,90293,

%T 63431,54477,118159,706053,1235351,3745117,7915039,9305013,13101671,

%U 37700557,79233519,126411173,375470391,1125156797,3708385599,11236128533,37078709511,112359569837

%N Multiply each term by 3 and erase the leftmost digit of the result: this leaves the sequence unchanged.

%C This is the lexicographically earliest sequence of distinct positive terms with this property.

%C If the erasure of the leftmost digit leaves one or more leading zeros in the result, erase also those zeros.

%H Alois P. Heinz, <a href="/A365986/b365986.txt">Table of n, a(n) for n = 1..2000</a>

%e a(1) = 1 and 3*1 = 3; erasing the leftmost digit 3 leaves nothing;

%e a(2) = 7 and 3*7 = 21; erasing the leftmost digit 2 leaves 1;

%e a(3) = 9 and 3*9 = 27; erasing the leftmost digit 2 leaves 7;

%e a(4) = 13 and 3*13 = 39; erasing the leftmost digit 3 leaves 9;

%e a(5) = 71 and 3*71 = 213; erasing the leftmost digit 2 leaves 13; etc.

%e We see that the last column of the above table is the sequence itself.

%p a:= proc(n) option remember; `if`(n=1, 1,

%p (t-> parse(cat(3-irem(t,3),t))/3)(a(n-1)))

%p end:

%p seq(a(n), n=1..35); # _Alois P. Heinz_, Sep 24 2023

%Y Cf. A365987, A317591.

%K nonn,base,easy

%O 1,2

%A _Eric Angelini_, Sep 24 2023

%E More terms from _Alois P. Heinz_, Sep 24 2023

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Last modified August 11 14:00 EDT 2024. Contains 375069 sequences. (Running on oeis4.)