A329004 a(n) is the largest index in [n] that maximizes tau.

1, 2, 3, 4, 4, 6, 6, 8, 8, 10, 10, 12, 12, 12, 12, 12, 12, 18, 18, 20, 20, 20, 20, 24, 24, 24, 24, 24, 24, 30, 30, 30, 30, 30, 30, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 72

Offset

1,2

Links

Peter Andrew, Table of n, a(n) for n = 1..20000

Formula

a(n) = n <=> n in { A067128 }. - Alois P. Heinz, Jun 11 2020

Maple

a:= proc(n) option remember; uses numtheory; `if`(n=1, 1,
      (t-> `if`(tau(n)<tau(t), t, n))(a(n-1)))
    end:
seq(a(n), n=1..100);  # Alois P. Heinz, Jun 11 2020

Mathematica

dmax = 0; nmax = 1; seq = {}; Do[If[(d = DivisorSigma[0, n]) >= dmax, dmax = d; nmax = n]; AppendTo[seq, nmax], {n, 1, 72}]; seq (* Amiram Eldar, Jun 11 2020 *)

Prog

(Haskell) a329004 = map fst $ scanl1 (\x y -> maximumBy (comparing snd) [x, y]) $ zip [1..] a000005

Crossrefs

Cf. A000005, A067128.

Sequence in context: A111939 A253248 A341112 * A003962 A102443 A102441

Adjacent sequences: A329001 A329002 A329003 * A329005 A329006 A329007

Keyword

nonn

Author

Peter Andrew, Jun 10 2020

Status

approved