

A117506


Irregular triangle read by rows: dimensions of the irreducible representations of the symmetric group S_n.


26



1, 1, 1, 1, 1, 2, 1, 1, 3, 2, 3, 1, 1, 4, 5, 6, 5, 4, 1, 1, 5, 9, 5, 10, 16, 5, 10, 9, 5, 1, 1, 6, 14, 14, 15, 35, 21, 21, 20, 35, 14, 15, 14, 6, 1, 1, 7, 20, 28, 14, 21, 64, 70, 56, 42, 35, 90, 56, 70, 14, 35, 64, 28, 21, 20, 7, 1
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OFFSET

0,6


COMMENTS

The nth row has partition(n) = A000041(n) entries.
Also the numbers of standard Young tableaux for Young diagrams (or partitions).
Also "generalized" Catalan numbers. For a partition of n, n=(n_1+...+n_d), this is the number of integral lattice paths from (0,...,0) to (n_1,...,n_d) such that for any point p=(p_1,...p_d) on such a path p_i is never less than p_j whenever i<j.  Graham H. Hawkes, Jul 05 2013
The irreducible representations of S_n correspond to Young diagrams or partitions.
Partitions of n are ordered according to AbramowitzStegun (ASt) (see the reference, pp. 8312). In contrast to ASt, a partition has nondecreasing parts (reverse notation of ASt).
The dimension of a representation of S_n corresponding to a Young diagram or partition is a(n,k) for the kth partition of n in this ASt order.
One could call these numbers a(n,k) M_4 (similar to M_0, M_1, M_2, M_3 given in A111786, A036038, A036039, A036040, respectively).
From Wolfdieter Lang, Oct 09 2015: (Start)
The first formula given below appears in A. Young, Q.S.A. III, PLMS 28 (1928) 255292 (third paper on "On Quantitative Substitutional Analysis"), Theorem II on p. 260, and he calls it f; see the collected papers (CP) reference, p. 357. Note the shorthand notation for the products; see Q.S.A. II, PLMS 34 (1902) 361397, p. 366, CP, p. 97, for the explicit one.
This formula also can be found in the GlassNg link, Theorem 1, p. 702, using the Vandermonde determinant in the numerator and reindexing the denominator.
The product of the hook length numbers, called H(n, k) in this formula below, is found in A263003(n, k).
The squared row entries sum to n!. See A. Young, Q.S.A. II (see above), pp. 367368, CP pp. 9899. Also Q.S.A. III, p. 265, CP p. 362.
(End)


REFERENCES

G. de B. Robinson (ed.), The Collected Papers of Alfred Young 18731940, University of Toronto Press, 1977.
G. B. Wybourne, Symmetry principles and atomic spectroscopy, Wiley, New York, 1970, p. 9.


LINKS

Alois P. Heinz, Rows n = 0..30, flattened
M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy].
A. M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, pp. 8312.
Kenneth Glass and ChiKeung Ng, A Simple Proof of the Hook Length Formula , Am. Math. Monthly 111 (2004) 700  704.
Graham H. Hawkes, An Elementary Proof of a Formula for SYT, arXiv preprint arXiv:1310.5919, 2013
Wolfdieter Lang, First 15 rows.
Eric Weisstein's World of Mathematics, Hook length formula.
Doron Zeilberger, Andre's Reflection Proof Generalized to the ManyCandidate Ballot Problem, Discrete Mathematics 44 (1983) 325326.
Index entries for sequences related to groups


FORMULA

a(n,k) = n!/H(n,k) with H(n,k):= Product_{i=1..m(n,k)} (x_i)!/Det(x_i^(m(n,k)j)) with the Vandermonde determinant for the variables x_i:=lambda(n,k)_i + m(n,k)i, i,j=1..m(n,k) if m(n,k) is the number of parts of the kth partition of n, called lambda(n,k), in the ASt order (see above). Lambda(n,k)_i denotes the ith part of the partition lambda(n,k), sorted in decreasing order (this is the reverse of the ASt notation).
a(n,k) = n!/Product_{j=1..n}(h(n,k,j) with the hook numbers h(n,k,j) of the Young diagram of the partition lambda(n,k) in the ASt order. See the link for 'hook length formula'.


EXAMPLE

[1];
[1];
[1, 1];
[1, 2, 1];
[1, 3, 2, 3, 1];
[1, 4, 5, 6, 5, 4, 1];
[1, 5, 9, 5, 10, 16, 5, 10, 9, 5, 1];...
a(4,4)=3 because the 4th partition of n=4 in ASt order is [2,1,1],
and H(4,4)=(4!*2!*1!)/Vandermonde([4,2,1]) = (4!*2)/6 =4*2, hence
4!/H(4,4) = 3.
a(4,4)=3 because the hook lengths of the Young diagram of [2,1,1] are [4, 1; 2; 1], hence 4!/(4*1*2*1) = 3.
The sum of the squared entries of each row gives n!: n = 5: 2*(1^1 + 4^2 + 5^2) + 6^2 = 120 = 5!.  Wolfdieter Lang, Oct 09 2015


MAPLE

h:= l> (n> mul(mul(1+l[i]j+add(`if`(l[k]>=j, 1, 0),
k=i+1..n), j=1..l[i]), i=1..n))(nops(l)):
g:= (n, i, l)> `if`(n=0 or i=1, [h([l[], 1$n])],
[g(n, i1, l)[], g(ni, min(ni, i), [l[], i])[]]):
T:= n> map(x> n!/x, g(n$2, []))[]:
seq(T(n), n=0..10); # Alois P. Heinz, Nov 05 2015


MATHEMATICA

h[l_List] := Function[n, Product[Product[1 + l[[i]]  j + Sum[If[l[[k]] >= j, 1, 0], {k, i+1, n}], {j, 1, l[[i]]}], {i, 1, n}]][Length[l]]; g[n_, i_, l_List] := If[n==0  i==1, Join[{h[Join[l, Array[1&, n]]]}], If[i<1, {}, Join[{g[n, i1, l]}, If[i>n, {}, g[ni, i, Join[l, {i}]]]]]] // Flatten; T[n_] := n!/ g[n, n, {}]; Table[T[n], {n, 0, 10}] // Flatten (* JeanFrançois Alcover, Dec 19 2015, after Alois P. Heinz *)


CROSSREFS

Cf. A000041, A000085 (row sums), A060240 (rows sorted), A263003.
Sequence in context: A006843 A324797 A049456 * A179205 A055089 A060117
Adjacent sequences: A117503 A117504 A117505 * A117507 A117508 A117509


KEYWORD

nonn,easy,tabf


AUTHOR

Wolfdieter Lang, Apr 13 2006


EXTENSIONS

Row n=0 prepended by Alois P. Heinz, Nov 05 2015


STATUS

approved



