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 A167524 Lexicographically smallest sequence which lists the position of the odd digits in the concatenation of its terms. 0

%I

%S 1,4,6,7,8,9,11,12,13,15,17,19,30,40,42,46,48,49,60,62,64,66,67

%N Lexicographically smallest sequence which lists the position of the odd digits in the concatenation of its terms.

%e We have a(1)=1 <=> the sequence starts with an odd digit.

%e a(2) can't be 2 (since this would place an even digit in position 2 and at the same time state that there's an odd digit), nor can it be 3 (since then the second odd digit would be in position 2 and not in position a(2)). But a(2)=4 is possible.

%e This implies that there follows another even digit, a(3)=6, before the next odd digit, a(4)=7, etc.

%e ______________________ 1 _________________ 2 _________________ 3 _________________ 4

%e pos. 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 ...

%e seq. 1,4,6,7,8,9,1 1,1 2,1 3,1 5,1 7,1 9,3 0,4 0,4 2,4 6,4 8,4 9,6 0,6 2,6 4,6 6,6 7,...

%K base,more,nonn

%O 1,2

%A _M. F. Hasler_, Nov 21 2009

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