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%I #11 Jan 23 2023 12:41:41
%S 1,6,15,28,45,66,91,128,162,200,231,372,325,406,495,656,561,954,703,
%T 1180,987,1078,1035,1896,1375,1534,1701,2324,1653,3090,1891,3104,2541,
%U 2686,3045,5004,2701,3382,3627,5560,3321,6846,3655,6028,6165,5014,4371
%N Main diagonal of array in A163280.
%p A033676 := proc(n) local a, d; a := 0 ; for d in numtheory[divisors](n) do if d^2 <= n then a := max(a, d) ; end if; end do: a; end proc: A163280 := proc(n, k) local r, T ; r := 0 ; for T from k^2 by k do if A033676(T) = k then r := r+1 ; if r = n then RETURN(T) ; end if; end if; end do: end proc: A164000 := proc(n) A163280(n,n) ; end proc: seq(A164000(n),n=1..60) ; # _R. J. Mathar_, Feb 16 2010
%t nmax = 50;
%t pm = Prime[nmax];
%t selDiv[n_] := Select[Divisors[n], #^2 <= n&][[-1]];
%t Clear[col];
%t col[k_] := col[k] = Select[Range[k pm], selDiv[#] == k&];
%t a[n_] := col[n][[n]];
%t Array[a, nmax] (* _Jean-François Alcover_, Mar 24 2020 *)
%o (PARI) lista(nn) = my(v = apply(f, [1..(2*nn-1)^2]), cols = vector(nn, i, select(x->(x==i), v, 1))); vector(nn, i, cols[i][i]); \\ _Michel Marcus_, Jan 23 2023
%Y Cf. A008578, A161344, A161345, A163280.
%K nonn
%O 1,2
%A _Omar E. Pol_, Aug 08 2009
%E Terms from a(13) on by _R. J. Mathar_, Feb 16 2010
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