

A243748


Triangle T(n,d): the number of subgroups of order d of the symmetric group S_n as d runs through the divisors of n!.


2



1, 1, 1, 1, 3, 1, 1, 1, 9, 4, 7, 4, 3, 1, 1, 1, 25, 10, 35, 6, 30, 15, 6, 15, 0, 6, 5, 0, 0, 1, 1, 1, 75, 40, 255, 36, 280, 255, 10, 36, 150, 0, 45, 50, 36, 90, 0, 30, 0, 0, 30, 12, 10, 0, 0, 12, 0, 0, 0, 1, 1, 1, 231, 175, 1295, 126, 1645, 120, 1575, 70, 378, 1715, 120, 0, 315, 350, 378, 120, 1435, 0, 0, 0, 245, 126, 120, 0
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OFFSET

1,5


COMMENTS

The columns skip the subgroups of S_n which are known not to exist (because their order does not divide the order of S_n, n!). This is just a reduction of rows in the triangle by omitting a large number of zeros.


LINKS

Table of n, a(n) for n=1..86.


EXAMPLE

There are T(3,2)=3 subgroups of S_3 of order 2, namely the groups generated by the permutations (1,2), (1,3) or (2,3).
1;
1,1;
1,3,1,1;
1,9,4,7,4,3,1,1;
1,25,10,35,6,30,15,6,15,0,6,5,0,0,1,1;


PROG

(GAP 4) LoadPackage("SONATA") ;;
Print("\n") ;
N := Factorial(7) ;; # adjusted to the maximum n below
subS := EmptyPlist(N) ;;
for n in [1..7] do
for e in [1..N] do
subS[e] := 0 ;
od;
g := SymmetricGroup(n) ;
sg := Size(g) ;
alls := Subgroups(g) ;
for s in alls do
o := Size(s) ;
if o <= N then
subS[o] := subS[o]+1 ;;
fi;
od ;
for d in [1..N] do
if ( sg mod d ) = 0 then
Print(subS[d], ", ") ;
fi;
od;
Print("\n") ;
od;


CROSSREFS

Cf. A005432 (row sums), A001189 (column d=2), A027423 (row lengths), A218913, A277566, A284210.
Sequence in context: A229142 A156535 A327564 * A340149 A340075 A307847
Adjacent sequences: A243745 A243746 A243747 * A243749 A243750 A243751


KEYWORD

nonn,tabf


AUTHOR

R. J. Mathar, Jun 09 2014


STATUS

approved



