A035004 - OEIS

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A035004

Number of divisors of the n-th nonprime.

1, 3, 4, 4, 3, 4, 6, 4, 4, 5, 6, 6, 4, 4, 8, 3, 4, 4, 6, 8, 6, 4, 4, 4, 9, 4, 4, 8, 8, 6, 6, 4, 10, 3, 6, 4, 6, 8, 4, 8, 4, 4, 12, 4, 6, 7, 4, 8, 6, 4, 8, 12, 4, 6, 6, 4, 8, 10, 5, 4, 12, 4, 4, 4, 8, 12, 4, 6, 4, 4, 4, 12, 6, 6, 9, 8, 8, 8, 4, 12, 8, 4, 10, 8, 4, 6, 6, 4, 4, 16, 3, 4, 4, 6, 4, 12, 8, 4

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OFFSET

1,2

COMMENTS

a(n+1) = a(n) only when a(n) is even. Will these repeat terms include each even integer >= 4? (See also A075036.) - Bill McEachen, Nov 16 2021

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = A000005(A018252(n)). - Omar E. Pol, Jan 31 2013

MATHEMATICA

DivisorSigma[0, Select[Range[200], !PrimeQ[#]&]] (* Harvey P. Dale, Mar 07 2016 *)

PROG