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 A227955 Triangle read by rows, T(n, k) = prime(1)^p(k,1)*...*prime(n)^p(k,n) where p(k,j) is the j-th part of the k-th partition of n. The partitions of n are ordered in reversed lexicographic order read from left-to-right, starting with [1,1,...1] going down to [n]. 2
 1, 2, 6, 4, 30, 12, 8, 210, 60, 36, 24, 16, 2310, 420, 180, 120, 72, 48, 32, 30030, 4620, 1260, 900, 840, 360, 216, 240, 144, 96, 64, 510510, 60060, 13860, 6300, 9240, 2520, 1800, 1080, 1680, 720, 432, 480, 288, 192, 128, 9699690, 1021020, 180180, 69300, 44100 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS The sequence can be seen as an encoding of Young's lattice (see the links). The ordering of Young's lattice is such that for two Young diagrams s, t, we have s <= t if and only if the Young diagram of s fits entirely inside the Young diagram of t (when the two diagrams are arranged so their lower-left corners coincide.) This order translates to our encoding as the divisibility relation. The number corresponding to s divides the number corresponding to t if and only if s <= t. The partition corresponding to a number can be recovered as the exponents of the primes in the prime factorization of the number. LINKS Peter Luschny, Rows n = 0..25, flattened Peter Luschny, Young's lattice (diagram) Peter Luschny, Integer partition trees Wikipedia, Young's lattice EXAMPLE For instance the partitions of 4 are ordered [1,1,1,1], [2,1,1,0], [2,2,0,0], [3,1,0,0], [4,0,0,0]. Consider the partition P = (3,2,1,1) written as a Young diagram (in French notation):     [ ]     [ ]     [ ][ ]     [ ][ ][ ] Next replace the boxes at the bottom line by the sequence of primes and write the number of boxes in the same column as exponents; then multiply. 2^4*3^2*5^1 = 720. 720 will appear in line 7 of the triangle (because P is a partition of 7) at position 10 (because the sequence of exponents [4, 2, 1] is the 10th partition in the order of partitions which we assume). [0]     1, [1]     2, [2]     6,    4, [3]    30,   12,    8, [4]   210,   60,   36,  24,  16, [5]  2310,  420,  180, 120,  72,  48,  32, [6] 30030, 4620, 1260, 900, 840, 360, 216, 240, 144, 96, 64. MAPLE with(combinat): A227955_row := proc(n) local e, w, p; p := [seq(ithprime(i), i=1..n)]; w := e -> mul(p[i]^e[nops(e)-i+1], i=1..nops(e)); seq(w(e), e = partition(n)) end: seq(print(A227955_row(i)), i=0..8); PROG (Sage) def A227955_row(n):     L = []     P = primes_first_n(n)     for p in Partitions(n):         L.append(mul(P[i]^p[i] for i in range(len(p))))     return L[::-1] for n in (0..8): A227955_row(n) CROSSREFS Reversed rows: A036035, row sums: A074140. Sequence in context: A073039 A253588 A228099 * A064538 A002790 A108951 Adjacent sequences:  A227952 A227953 A227954 * A227956 A227957 A227958 KEYWORD nonn,tabf AUTHOR Peter Luschny, Aug 01 2013 STATUS approved

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Last modified September 26 15:27 EDT 2017. Contains 292531 sequences.