A164000 Main diagonal of array in A163280.

1, 6, 15, 28, 45, 66, 91, 128, 162, 200, 231, 372, 325, 406, 495, 656, 561, 954, 703, 1180, 987, 1078, 1035, 1896, 1375, 1534, 1701, 2324, 1653, 3090, 1891, 3104, 2541, 2686, 3045, 5004, 2701, 3382, 3627, 5560, 3321, 6846, 3655, 6028, 6165, 5014, 4371

Offset

1,2

Links

Table of n, a(n) for n=1..47.

Maple

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

Mathematica

nmax = 50;
pm = Prime[nmax];
selDiv[n_] := Select[Divisors[n], #^2 <= n&][[-1]];
Clear[col];
col[k_] := col[k] = Select[Range[k pm], selDiv[#] == k&];
a[n_] := col[n][[n]];
Array[a, nmax] (* Jean-François Alcover, Mar 24 2020 *)

Prog

(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

Crossrefs

Cf. A008578, A161344, A161345, A163280.

Sequence in context: A081873 A096892 A000384 * A212087 A301292 A359696

Adjacent sequences: A163997 A163998 A163999 * A164001 A164002 A164003

Keyword

nonn

Author

Omar E. Pol, Aug 08 2009

Extensions

Terms from a(13) on by R. J. Mathar, Feb 16 2010

Status

approved