A146288 - OEIS

A146288

Number of divisors of the n-th prime signature number (A025487(n)).

1, 2, 3, 4, 4, 6, 5, 8, 8, 6, 9, 10, 12, 7, 12, 12, 16, 8, 15, 18, 14, 16, 16, 20, 9, 18, 24, 16, 24, 20, 24, 10, 21, 30, 18, 32, 24, 27, 28, 11, 32, 24, 36, 25, 36, 20, 40, 28, 36, 32, 12, 40, 27, 32, 48, 30, 42, 22, 48, 32, 45, 36, 13, 48, 30, 48, 60, 35, 48, 48, 24, 54, 50, 56

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OFFSET

1,2

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A000005(A025487(n)).

EXAMPLE

a(4) = 4 because 4 positive integers divide evenly into A025487(4) = 6: 1, 2, 3 and 6.

MATHEMATICA

s = {1}; Do[If[GreaterEqual @@ (f = FactorInteger[n])[[;; , 2]] && PrimePi[f[[-1, 1]]] == Length[f], AppendTo[s, DivisorSigma[0, n]]], {n, 2, 10000}]; s (* Amiram Eldar, Aug 05 2024 *)

PROG

(Haskell)

a146288 = a000005 . a025487 -- Reinhard Zumkeller, Sep 17 2014

CROSSREFS

a(n) = sum of the n-th row of A146290, A146292.

A rearrangement of A080444.

Cf. A000005 (number of divisors), A025487.

Sequence in context: A373624 A343292 A079788 * A244361 A199424 A350634

Adjacent sequences: A146285 A146286 A146287 * A146289 A146290 A146291

KEYWORD

nonn

AUTHOR

Matthew Vandermast, Nov 11 2008

STATUS

approved