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 A241918 Table of partitions where the ordering is based on the modified partial sums of the exponents of primes in the prime factorization of n. 15

%I

%S 0,1,1,1,2,1,1,1,2,2,1,1,1,1,3,1,2,2,2,2,1,1,1,1,1,3,3,1,1,1,1,1,1,2,

%T 2,2,2,1,2,2,4,1,1,1,1,1,1,1,2,3,1,1,1,1,1,1,1,1,3,3,3,1,2,2,2,2,2,2,

%U 2,2,1,1,1,1,1,1,1,1,1,4,4,1,1,2,2,2,2,2,2,2,1,3,3,3,3,3,1,1,1,1,1,1,1,1,1,1,2,3,3,1,1,1,1,1,1,1,1,1,1,1,5

%N Table of partitions where the ordering is based on the modified partial sums of the exponents of primes in the prime factorization of n.

%C a(1) = 0 by convention (stands for an empty partition).

%C For n >= 2, A203623(n-1)+2 gives the index to the beginning of row n and for n>=1, A203623(n)+1 is the index to the end of row n.

%H Antti Karttunen, <a href="/A241918/b241918.txt">Table of n, a(n) for n = 1..10081; rows 1..521 flattened.</a>

%H <a href="http://oeis.org/wiki/User:Antti_Karttunen/Mail_by_Marc_LeBrun_Re_Partition_ordering_on_SeqFan_list_posted_12_Jan_2006">Marc LeBrun's original "crazy order" mapping for partitions</a> (Copy of Marc's Jan 11 2006 message in OEIS Wiki)

%F If A241914(n)=0 and A241914(n+1)=0, a(n) = A067255(n); otherwise, if A241914(n)=0 and A241914(n+1)>0, a(n) = A067255(n)+1; otherwise, if A241914(n)>0 and A241914(n+1)=0, a(n) = a(n-1) + A067255(n) - 1, otherwise, when A241914(n)>0 and A241914(n+1)>0, a(n) = a(n-1) + A067255(n).

%e Table begins:

%e Row Partition

%e [ 1] 0; (stands for empty partition)

%e [ 2] 1; (as 2 = 2^1)

%e [ 3] 1,1; (as 3 = 2^0 * 3^1)

%e [ 4] 2; (as 4 = 2^2)

%e [ 5] 1,1,1; (as 5 = 2^0 * 3^0 * 5^1)

%e [ 6] 2,2; (as 6 = 2^1 * 3^1)

%e [ 7] 1,1,1,1; (as 7 = 2^0 * 3^0 * 5^0 * 7^1)

%e [ 8] 3; (as 8 = 2^3)

%e [ 9] 1,2; (as 9 = 2^0 * 3^2)

%e  2,2,2; (as 10 = 2^1 * 3^0 * 5^1)

%e  1,1,1,1,1;

%e  3,3;

%e  1,1,1,1,1,1;

%e  2,2,2,2;

%e  1,2,2; (as 15 = 2^0 * 3^1 * 5^1)

%e  4;

%e  1,1,1,1,1,1,1;

%e  2,3; (as 18 = 2^1 * 3^2)

%e etc.

%e If n is 2^k (k>=1), then the partition is a singleton {k}, otherwise, add one to the exponent of 2 (= A007814(n)), and subtract one from the exponent of the greatest prime dividing n (= A071178(n)), leaving the intermediate exponents as they are, and then take partial sums of all, thus resulting for e.g. 15 = 2^0 * 3^1 * 5^1 the modified sequence of exponents {0+1, 1, 1-1} -> {1,1,0}, whose partial sums {1,1+1,1+1+0} -> {1,2,2} give the corresponding partition at row 15.

%t Table[If[n == 1, {0}, Function[s, Function[t, Accumulate[If[Length@ t < 2, {0}, Join[{1}, ConstantArray[0, Length@ t - 2], {-1}]] + ReplacePart[t, Map[#1 -> #2 & @@ # &, s]]]]@ ConstantArray[0, Transpose[s][[1, -1]]]][FactorInteger[n] /. {p_, e_} /; p > 0 :> {PrimePi@ p, e}]], {n, 31}] // Flatten (* _Michael De Vlieger_, May 12 2017 *)

%o (Scheme, with _Antti Karttunen_'s IntSeq-library)

%o (definec (A241918 n) (cond ((zero? (A241914 n)) (if (zero? (A241914 (+ n 1))) (A067255 n) (+ 1 (A067255 n)))) ((zero? (A241914 (+ 1 n))) (+ (A241918 (- n 1)) (- (A067255 n) 1))) (else (+ (A241918 (- n 1)) (A067255 n)))))

%Y For n>=2, the length of row n is given by A061395(n).

%Y Cf. also A067255, A203623, A241914.

%Y Other tables of partitions: A112798 (also based on prime factorization), A227739, A242628 (encoded in the binary representation of n), and A036036-A036037, A080576-A080577, A193073 for various lexicographical orderings.

%Y Permutation A241909 maps between order of partitions employed here, and the order employed in A112798.

%Y Permutation A122111 is induced when partitions in this list are conjugated.

%Y A241912 gives the row numbers for which the corresponding rows in A112798 and here are the conjugate partitions of each other.

%K nonn,tabf

%O 1,5

%A _Antti Karttunen_, May 03 2014, based on _Marc LeBrun_'s Jan 11 2006 message on SeqFan mailing list.

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Last modified September 29 14:13 EDT 2020. Contains 337431 sequences. (Running on oeis4.)