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A225642 Irregular table read by rows: n-th row gives distinct values of successively iterated Landau-like functions for n, starting with the initial value n.

%I A225642 #38 Mar 13 2018 04:09:10
%S A225642 1,2,3,6,4,12,5,30,60,6,30,60,7,84,420,8,120,840,9,180,1260,2520,10,
%T A225642 210,840,2520,11,330,4620,13860,27720,12,420,4620,13860,27720,13,780,
%U A225642 8580,60060,180180,360360,14,630,8190,90090,360360,15,840,10920,120120,360360
%N A225642 Irregular table read by rows: n-th row gives distinct values of successively iterated Landau-like functions for n, starting with the initial value n.
%C A225642 The leftmost column of table (the initial term of each row, T(n,1)) is n, corresponding to lcm(n) computed from the singular {n} partition of n, after which, on the same row, each further term T(n,i) is computed by finding such a partition {p_1 + p_2 + ... + p_k} of n so that value of lcm(T(n, i-1), p_1, p_2, ..., p_k) is maximized, until finally A003418(n) is reached, which will be listed as the last term of row n (as the result would not change after that, if we continued the same process).
%C A225642 Of possible interest: which numbers occur only once in this table, and which occur multiple times? And how many times, if each number occurs only a finite number of times?
%C A225642 Each number occurs a finite number of times: rows are increasing, first column is increasing, so n will occur last in row n, leftmost column. Primes (and other numbers too) occur once. - _Alois P. Heinz_, May 25 2013
%H A225642 Alois P. Heinz, <a href="/A225642/b225642.txt">Rows n = 1..150, flattened</a>
%e A225642 The first fifteen rows of table are:
%e A225642    1;
%e A225642    2;
%e A225642    3,   6;
%e A225642    4,  12;
%e A225642    5,  30,    60;
%e A225642    6,  30,    60;
%e A225642    7,  84,   420;
%e A225642    8, 120,   840;
%e A225642    9, 180,  1260,   2520;
%e A225642   10, 210,   840,   2520;
%e A225642   11, 330,  4620,  13860,  27720;
%e A225642   12, 420,  4620,  13860,  27720;
%e A225642   13, 780,  8580,  60060, 180180, 360360;
%e A225642   14, 630,  8190,  90090, 360360;
%e A225642   15, 840, 10920, 120120, 360360;
%t A225642 b[n_, i_] := b[n, i] = If[n == 0, {1}, If[i < 1, {}, Table[Map[Function[{x}, LCM[x, If[j == 0, 1, i]]], b[n - i * j, i - 1]], {j, 0, n/i}]]]; T[n_] := T[n] = Module[{d, h, t, lis}, t = b[n, n]; lis = {}; d = n; h = 0; While[d != h, AppendTo[lis, d]; h = d; d = Max[Table[LCM[h, i], {i, t}]]]; lis]; Table[T[n], {n, 1, 20}] // Flatten (* _Jean-François Alcover_, Mar 02 2016, after _Alois P. Heinz_ *)
%o A225642 (Scheme with _Antti Karttunen_'s IntSeq-library):
%o A225642 (definec (A225642 n) (A225640bi (Aux_for_225642 n) (- n (A225645 (Aux_for_225642 n))))) ;; Scheme-definition of A225640bi given in A225640.
%o A225642 (define Aux_for_225642 (COMPOSE -1+ (LEAST-GTE-I 1 1 A225645) 1+)) ;; Auxiliary function not submitted separately, which gives the row-number for the n-th term.
%o A225642 ;; It starts as 1, 2, 3, 3, 4, 4, 5, 5, 5, 6, 6, 6, 7, 7, 7, 8, 8, 8, 9, 9, 9, 9, 10, 10, 10, 10, 11, 11, 11, 11, 11, ...
%Y A225642 Cf. A225644 (length of n-th row), A225646 (for n >= 3, second term of n-th row).
%Y A225642 Cf. A003418 (largest and rightmost term of n-th row).
%Y A225642 Cf. A225640, A225641, A225645.
%Y A225642 Cf. A225632 (each row starts with 1 instead of n).
%Y A225642 Cf. A226055 (the first common term with A225632 on the n-th row).
%Y A225642 Cf. A225639 (distance to that first common term).
%Y A225642 Cf. A226056 (number of trailing common terms with A225632 on the n-th row).
%K A225642 nonn,tabf
%O A225642 1,2
%A A225642 _Antti Karttunen_, May 15 2013