A104361 - OEIS

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A104361

Number of divisors of A104357(n) = A104350(n) - 1.

1, 2, 2, 2, 2, 2, 4, 2, 2, 2, 4, 4, 4, 4, 2, 4, 8, 8, 2, 8, 8, 8, 2, 4, 16, 16, 4, 4, 32, 16, 4, 8, 4, 8, 2, 8, 16, 8, 32, 8, 16, 16, 32, 2, 8, 16, 4, 4, 4, 8, 2, 4, 8, 4, 8, 2, 16, 2, 8, 16, 64, 16, 16, 4, 64, 2, 32, 16, 16, 2, 4, 32, 128, 16, 32, 8, 16, 16, 32, 16, 32, 4, 16, 16, 32, 8, 8, 8, 4, 32, 4, 32, 16, 128, 4, 32, 8, 4

(list; graph; refs; listen; history; text; internal format)

OFFSET

2,2

LINKS

Max Alekseyev, Table of n, a(n) for n = 2..145

Reinhard Zumkeller, Products of largest prime factors of numbers <= n

FORMULA

a(n) = A000005(A104357(n)).

MATHEMATICA

a[n_] := DivisorSigma[0, -1 + Product[FactorInteger[k][[-1, 1]], {k, 1, n}]]; Array[a, 50, 2] (* Amiram Eldar, Feb 12 2020 *)

CROSSREFS