OFFSET
1,4
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..14
EXAMPLE
The first 5 terms of {r(k)} are: 1,1,2,4/3,25/18. The continued fraction, whose terms are the permutation of the first 5 terms of {r(k)} which leads to the smallest r(6), is [1;2,1,25/18,4/3] = 416/303.
MAPLE
Ltoc := proc(L) numtheory[nthconver](L, nops(L)-1) ; end: r := proc(n) option remember ; local m, rL, rp, L ; if n = 1 then 1; else rL := [seq(procname(i), i=1..n-1)] ; rp := combinat[permute](rL) ; m := Ltoc(rL) ; for L in rp do m := min(m, Ltoc(L)) ; od: m ; fi; end: A128775 := proc(n) denom(r(n)) ; end: for n from 1 do printf("%d, \n", A128775(n)) ; od: # R. J. Mathar, Jul 30 2009
tor:= proc(l) local j; infinity; for j from nops(l) to 1 by -1 do l[j]+1/% od end: hs:= proc(l) local ll, h, s, m; ll:= []; h:= nops(l); s:= 1; m:= s; while s<=h do ll:= [ll[], l[m]]; if m=h then h:= h-1; m:= s else s:= s+1; m:= h fi od; ll end: r:= proc(n) option remember; local j; `if`(n=1, 1, tor(hs(sort([seq(r(j), j=1..n-1)])))) end: a:= n-> denom(r(n)): seq(a(n), n=1..12); # Alois P. Heinz, Aug 04 2009
MATHEMATICA
r[1] = r[2] = 1;
r[n_] := r[n] = FromContinuedFraction /@ Permutations[Array[r, n-1]] // Min;
Table[a[n] = Denominator[r[n]]; Print[n, " ", a[n]]; a[n], {n, 1, 11}] (* Jean-François Alcover, May 20 2020 *)
CROSSREFS
KEYWORD
frac,nonn
AUTHOR
Leroy Quet, Mar 27 2007
EXTENSIONS
3 more terms from R. J. Mathar, Jul 30 2009
a(10)-a(11) from Alois P. Heinz, Aug 04 2009
STATUS
approved