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A060310 a(1)=1, a(2)=3; then append digits of a(n-1)*a(n).

%I A060310 #16 Aug 18 2025 11:56:49
%S A060310 1,3,3,9,2,7,1,8,1,4,7,8,8,4,2,8,5,6,6,4,3,2,8,1,6,4,0,3,0,3,6,2,4,1,
%T A060310 2,6,1,6,8,6,2,4,0,0,0,0,1,8,1,2,8,4,2,1,2,6,6,4,8,4,8,1,2,8,0,0,0,0,
%U A060310 0,8,8,2,1,6,3,2,8,2,2,1,2,3,6,2,4,3,2,3,2,3,2,8,2,1,6,0,0,0,0,0,0,6,4,1,6
%N A060310 a(1)=1, a(2)=3; then append digits of a(n-1)*a(n).
%H A060310 Paolo Xausa, <a href="/A060310/b060310.txt">Table of n, a(n) for n = 1..10000</a>
%e A060310 1*3=3, 3*3=9, 3*9=27, 9*2=18, ...
%t A060310 Fold[Join[#, IntegerDigits[Times @@ #[[#2;; #2+1]]]] &, {1, 3}, Range[100]] (* _Paolo Xausa_, Aug 18 2025 *)
%o A060310 (Python)
%o A060310 from itertools import islice
%o A060310 from collections import deque
%o A060310 def agen(): # generator of terms
%o A060310     a = deque([1, 3])
%o A060310     while True:
%o A060310         a.extend(list(map(int, str(a[0]*a[1]))))
%o A060310         yield a.popleft()
%o A060310 print(list(islice(agen(), 105))) # _Michael S. Branicky_, Aug 18 2025
%Y A060310 Cf. A045777, A093094, A093095, A093096, A093097, A096381.
%K A060310 nonn,base
%O A060310 1,2
%A A060310 _Jason Earls_, Mar 27 2001