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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 (list; graph; refs; listen; history; text; internal format)
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.
Is this (apart from the first term) the same as A103700? - R. J. Mathar, Feb 12 2024
LINKS
Éric Angelini and Giorgos Kalogeropoulos, The same sequence but differently, personal blog, Jan 24th 2024.
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, n-1]][[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)))
print(list(islice(agen(), 84))) # Michael S. Branicky, Jan 27 2024
CROSSREFS
Sequence in context: A063596 A360382 A284518 * A309660 A341821 A184959
KEYWORD
base,nonn
AUTHOR
STATUS
approved

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Last modified February 27 08:19 EST 2024. Contains 370367 sequences. (Running on oeis4.)