cp's OEIS Frontend

A369604 T is a "boomerang sequence": adding 9 to the 1st digit of T, 10 to the 2nd digit of T, 11 to the 3rd digit of T, 12 to the 4th digit of T, 13 to the 5th digit of T, 14 to the 6th digit of T, etc., and following each result with a comma leaves T unchanged.

%I A369604 #15 Feb 04 2024 18:07:39
%S A369604 10,10,12,12,14,16,16,18,18,22,20,26,22,28,24,32,26,34,29,30,31,30,33,
%T A369604 38,35,36,37,44,39,42,42,42,43,48,46,48,47,55,50,48,52,51,54,52,56,57,
%U A369604 58,64,60,63,62,66,64,69,67,68,68,75,71,70,73,72,75,74,77,77,79,84,81,84,83,88,85,89,88,89,90,86,91
%N A369604 T is a "boomerang sequence": adding 9 to the 1st digit of T, 10 to the 2nd digit of T, 11 to the 3rd digit of T, 12 to the 4th digit of T, 13 to the 5th digit of T, 14 to the 6th digit of T, etc., and following each result with a comma leaves T unchanged.
%C A369604 Lexicographically earliest sequence starting with a(1) = 10.
%H A369604 Éric Angelini and Giorgos Kalogeropoulos, <a href="https://cinquantesignes.blogspot.com/2024/01/the-same-sequence-but-differently.html">The same sequence but differently</a>, personal blog, Jan 24th 2024.
%e A369604 Adding  9 to 1 (the 1st digit of 10) gives 10
%e A369604 Adding 10 to 0 (the 2nd digit of 10) gives 10
%e A369604 Adding 11 to 1 (the 1st digit of 10) gives 12
%e A369604 Adding 12 to 0 (the 2nd digit of 10) gives 12
%e A369604 Adding 13 to 1 (the 1st digit of 12) gives 14
%e A369604 Adding 14 to 2 (the 2nd digit of 12) gives 16, etc.
%e A369604 We see that the last column above is the sequence T itself.
%t A369604 a[1]=10;a[n_]:=a[n]=Flatten[IntegerDigits/@Array[a,n-1]][[n]]+8+n;Array[a,100]
%o A369604 (Python)
%o A369604 from itertools import count, islice
%o A369604 def agen(): # generator of terms
%o A369604     an, digits = 10, [0]
%o A369604     for n in count(2):
%o A369604         yield an
%o A369604         an = n + 8 + digits.pop(0)
%o A369604         digits += list(map(int, str(an)))
%o A369604 print(list(islice(agen(), 79))) # _Michael S. Branicky_, Jan 27 2024
%Y A369604 Cf. A103700, A369603, A369798, A369823, A369824.
%K A369604 base,nonn
%O A369604 1,1
%A A369604 _Eric Angelini_ and _Giorgos Kalogeropoulos_, Jan 27 2024