A014489 Positions of involutions (permutations whose square is the identity) in reverse colexicographic order (A055089/A195663).
0, 1, 2, 5, 6, 7, 14, 16, 21, 23, 24, 25, 26, 29, 54, 55, 60, 67, 80, 82, 86, 94, 105, 107, 111, 119, 120, 121, 122, 125, 126, 127, 134, 136, 141, 143, 264, 265, 266, 269, 288, 289, 314, 316, 339, 341, 390, 391, 396, 403, 414, 415, 444, 450, 469
Offset: 0
Keywords
Links
- Robert Israel, Table of n, a(n) for n = 0..3996
Crossrefs
Programs
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Maple
N:= 100: # to get a(0) to a(N) M:= 0: A[0]:= 0: count:= 0: for m from 2 while count < N do P:= remove(t -> t[1]=1, combinat:-permute(m)); P:= map(t -> ListTools:-Reverse(subs([seq(i=m+1-i,i=1..m)],t)),P); R:= select(t -> max(map(nops,convert(P[t],disjcyc))) = 2, [$1..nops(P)]); for r in R do count:= count+1; A[count]:= r+M; if count = N then break fi; od: M:= M + nops(P); od: seq(A[i],i=0..count); # Robert Israel, Oct 28 2015
Extensions
Name changed by Antti Karttunen, Aug 30 2015
Comments