

A369603


S is a "boomerang sequence": adding 9 to each digit of S and following the result with a comma leaves S unchanged.


4



10, 9, 18, 10, 17, 10, 9, 10, 16, 10, 9, 18, 10, 9, 10, 15, 10, 9, 18, 10, 17, 10, 9, 18, 10, 9, 10, 14, 10, 9, 18, 10, 17, 10, 9, 10, 16, 10, 9, 18, 10, 17, 10, 9, 18, 10, 9, 10, 13, 10, 9, 18, 10, 17, 10, 9, 10, 16, 10, 9, 18, 10, 9, 10, 15, 10, 9, 18, 10, 17, 10, 9, 10, 16, 10, 9, 18, 10, 17, 10, 9, 18, 10, 9
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OFFSET

1,1


COMMENTS

Lexicographically earliest sequence starting with a(1) = 10.
The only integers that appear in the sequence are 9, 10, 11, 12, 13, 14, 15, 16, 17 and 18.


LINKS



EXAMPLE

Adding 9 to 1 (the 1st digit of 10) gives 10
Adding 9 to 0 (the 2nd digit of 10) gives 9
Adding 9 to 9 (the only digit of 9) gives 18
Adding 9 to 1 (the 1st digit of 18) gives 10
Adding 9 to 8 (the 2nd digit of 18) gives 17, etc.
We see that the last column above is the sequence S itself.


MATHEMATICA

a[1]=10; a[n_]:=a[n]=Flatten[IntegerDigits/@Array[a, n1]][[n]]+9; Array[a, 100]


PROG

(Python)
from itertools import islice
def agen(): # generator of terms
an, digits = 10, [0]
while True:
yield an
an = 9 + digits.pop(0)
digits += list(map(int, str(an)))


CROSSREFS



KEYWORD

base,nonn


AUTHOR



STATUS

approved



