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A063008
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Canonical partition sequence (see A080577) encoded by prime factorization. The partition [p1,p2,p3,...] with p1 >= p2 >= p3 >= ... is encoded as 2^p1 * 3^p2 * 5^p3 * ... .
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35
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1, 2, 4, 6, 8, 12, 30, 16, 24, 36, 60, 210, 32, 48, 72, 120, 180, 420, 2310, 64, 96, 144, 240, 216, 360, 840, 900, 1260, 4620, 30030, 128, 192, 288, 480, 432, 720, 1680, 1080, 1800, 2520, 9240, 6300, 13860, 60060, 510510, 256, 384, 576, 960, 864, 1440, 3360
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OFFSET
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0,2
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COMMENTS
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Partitions are ordered first by sum. Then all partitions of n are viewed as exponent tuples on n variables and their corresponding monomials are ordered reverse lexicographically. This gives a canonical ordering: [] [1] [2,0] [1,1] [3,0,0] [2,1,0] [1,1,1] [4,0,0,0] [3,1,0,0] [2,2,0,0] [2,1,1,0] [1,1,1,1]... Rearrangement of A025487, A036035 etc.
Or, least integer of each prime signature; resorted in accordance with the integer partitions described in A080577. - Alford Arnold, Feb 13 2008
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LINKS
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FORMULA
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EXAMPLE
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Partition [2,1,1,1] for n=5 gives 2^2*3*5*7 = 420.
The sequence begins:
1;
2;
4, 6;
8, 12, 30;
16, 24, 36, 60, 210;
32, 48, 72, 120, 180, 420, 2310;
64, 96, 144, 240, 216, 360, 840, 900, 1260, 4620, 30030;
...
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MAPLE
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with(combinat): A063008_row := proc(n) local e, w, r;
r := proc(L) local B, i; B := NULL;
for i from nops(L) by -1 to 1 do
B := B, L[i] od; [%] end:
w := proc(e) local i, m, p, P; m := infinity;
P := permute([seq(ithprime(i), i=1..nops(e))]);
for p in P do m := min(m, mul(p[i]^e[i], i=1..nops(e))) od end:
[seq(w(e), e = r(partition(n)))] end:
# second Maple program:
b:= (n, i)-> `if`(n=0 or i=1, [[1$n]], [map(x->
[i, x[]], b(n-i, min(n-i, i)))[], b(n, i-1)[]]):
T:= n-> map(x-> mul(ithprime(i)^x[i], i=1..nops(x)), b(n$2))[]:
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MATHEMATICA
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row[n_] := Product[ Prime[k]^#[[k]], {k, 1, Length[#]}]& /@ IntegerPartitions[n]; Table[row[n], {n, 0, 8}] // Flatten (* Jean-François Alcover, Dec 10 2012 *)
b[n_, i_] := b[n, i] = If[n == 0 || i == 1, {Table[1, {n}]}, Join[ Prepend[#, i]& /@ b[n - i, Min[n - i, i]], b[n, i - 1]]];
T[n_] := Product[Prime[i]^#[[i]], {i, 1, Length[#]}]& /@ b[n, n];
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CROSSREFS
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See A080576 Maple (graded reflected lexicographic) ordering.
See A080577 Mathematica (graded reverse lexicographic) ordering.
See A036036 "Abramowitz and Stegun" (graded reflected colexicographic) ordering.
See A036037 for graded colexicographic ordering.
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KEYWORD
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AUTHOR
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Antonio G. Astudillo (afg_astudillo(AT)hotmail.com), Jul 02 2001
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EXTENSIONS
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STATUS
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approved
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