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A358180 Indices for A358168.

%I A358180 #24 Nov 06 2022 01:40:29
%S A358180 1,30,162,1150,11603,104511,1041245,10226995,101514698,1008495923,
%T A358180 10060201866
%N A358180 Indices for A358168.
%C A358180 a(6)-a(7) from Chuck Gaydos.
%t A358180 nn = 2^20; q[_] = False; q[0] = True; a[_] = 0; c[_] = -1; c[0] = 2; m = 1; {1}~Join~Reap[Do[j = c[m]; a[n] = m; c[m] = n; m = 0; If[j > 0, m = n - j]; If[! q[#2], Sow[n]; q[#2] = True] & @@ {a[n], IntegerLength[a[n]]}, {n, 3, nn}] ][[-1, -1]] (* _Michael De Vlieger_, Nov 05 2022 *)
%o A358180 (Python)
%o A358180 from itertools import count
%o A358180 def A358180(n):
%o A358180     b, bdict, k = 0, {0:(1,)},10**(n-1) if n > 1 else 0
%o A358180     for m in count(2):
%o A358180         if b >= k:
%o A358180             return m-1
%o A358180         if len(l := bdict[b]) > 1:
%o A358180             b = m-1-l[-2]
%o A358180             if b in bdict:
%o A358180                 bdict[b] = (bdict[b][-1],m)
%o A358180             else:
%o A358180                 bdict[b] = (m,)
%o A358180         else:
%o A358180             b = 0
%o A358180             bdict[0] = (bdict[0][-1],m) # _Chai Wah Wu_, Nov 05 2022
%Y A358180 Cf. A181391, A358168.
%K A358180 nonn,hard,more
%O A358180 1,2
%A A358180 _G. L. Honaker, Jr._, Nov 02 2022
%E A358180 a(8) from _Michael De Vlieger_, Nov 05 2022
%E A358180 a(9)-a(10) from _Chai Wah Wu_, Nov 05 2022
%E A358180 a(11) from _Martin Ehrenstein_, Nov 05 2022