A372323 A124652(n) is the a(n)-th term in row A372111(n-1) of irregular triangle A162306.
2, 4, 4, 4, 5, 7, 5, 8, 8, 2, 10, 8, 12, 11, 13, 6, 13, 6, 6, 9, 8, 11, 4, 8, 16, 5, 6, 7, 13, 12, 7, 10, 19, 15, 16, 17, 9, 6, 15, 10, 3, 11, 8, 18, 28, 14, 14, 10, 30, 28, 15, 4, 20, 33, 13, 12, 6, 22, 18, 21, 12, 11, 29, 12, 11, 8, 24, 18, 8, 14, 17, 32, 33
Offset: 3
Keywords
Examples
Let b(x) = A124652(x) and let s(x) = A372111(x), where A372111 contains partial sums of A124652.
a(3) = 2 since b(3) = 3 is the 2nd term in row s(3) = 3 of A162306, {1, [3]}.
a(4) = 4 since b(4) = 4 is the 4th term in row s(4) = 6 of A162306, {1, 2, 3, [4], 6}.
a(5) = 4 since b(5) = 5 is T(s(n-1), 4) = T(10, 4), {1, 2, 4, [5], 8, 10}.
a(6) = 4 since b(6) = 9 is T(s(n-1), 4) = T(15, 4), {1, 3, 5, [9], 15}.
a(7) = 5 since b(7) = 6 is T(s(n-1), 5) = T(24, 5), {1, 2, 3, 4, [6], 8, 9, 12, 16, 18, 24}, etc.
Table relating this sequence to b = A124652, s = A372111, r = A372322, and A162306.
n b(n) s(n-1) a(n) r(n) row s(n-1) of A162306
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3 3 3 2 2 {1, [3]}
4 4 6 4 5 {1, 2, 3, [4], 6}
5 5 10 4 6 {1, 2, 4, [5], 8, 10}
6 9 15 4 5 {1, 3, 5, [9], 15}
7 6 24 5 11 {1, 2, 3, 4, [6], ..., 24}
8 8 30 7 18 {1, 2, 3, 4, 5, 6, [8], ..., 30}
9 16 38 5 8 {1, 2, 4, 8, [16], 19, 32, 38}
10 12 54 8 16 {1, 2, 3, 4, 6, 8, 9, [12], ..., 54}
11 11 66 8 22 {1, 2, 3, 4, 6, 8, 9, [11], ..., 66}
12 7 77 2 5 {1, [7], 11, 49, 77}
13 14 84 10 28 {1, 2, 3, 4, ..., 12, [14], ..., 84}
14 28 98 8 13 {1, 2, 4, 7, ..., 16, [28], ..., 98}
Links
- Michael De Vlieger, Table of n, a(n) for n = 3..10000
- Michael De Vlieger, Bar chart showing a(n)/A372322(n-1) for n = 3..1024. This chart illustrates the "depth" of A124652(n) among the terms of the A372111(n-1)-th row of A162306.
Programs
-
Mathematica
nn = 75; c[_] := False; rad[x_] := rad[x] = Times @@ FactorInteger[x][[All, 1]]; f[x_] := Select[Range[x], Divisible[x, rad[#]] &]; Array[Set[{a[#], c[#]}, {#, True}] &, 2]; s = a[1] + a[2]; Reap[Do[r = f[s]; k = SelectFirst[r, ! c[#] &]; Sow[FirstPosition[r, k][[1]]]; c[k] = True; s += k, {i, 3, nn}] ][[-1, 1]]
Comments