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`%I #18 Feb 24 2021 16:00:16
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`%S 1,11,112,11221,11221221,1122122122121,1122122122121221212111,
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`%T 1122122122121221212111221212111211113,
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`%U 1122122122121221212111221212111211113221212111211113211113141
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`%N Successive generations of A306211, in compressed notation.
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`%C "Compressed" means the separating commas have been omitted. This will only work as long as the terms of A306211 are at most 9. However, we know from Chaffin's work (see A306211) that this is true at least for the first 10228800161220 terms of A306211.
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`%t s[n_] := If[n == 1, {1}, s[n] = Join[s[n-1], Length /@ Split[s[n-1]]]];
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`%t a[n_] := FromDigits[s[n]];
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`%t Array[a, 9] (* _Jean-François Alcover_, Feb 24 2021 *)
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`%Y Cf. A306211, A306215 (lengths), A323478 (increments).
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`%K nonn,base
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`%O 1,2
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`%A _N. J. A. Sloane_, Jan 31 2019
`