A086299 - OEIS

A086299

a(n) = if n is 7-smooth then 1 else 0: characteristic function of 7-smooth numbers.

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 1, 0, 1, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1, 1, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0

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OFFSET

1,1

LINKS

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

Eric Weisstein's World of Mathematics, Smooth Number.

Index entries for characteristic functions.

FORMULA

Multiplicative with: a(p) = if p<=7 then 1 else 0, p prime.

a(A002473(n)) = 1; a(A068191(n)) = 0. - Reinhard Zumkeller, Apr 01 2012

Dirichlet g.f.: 1/((1-2^(-s))*(1-3^(-s))*(1-5^(-s))*(1-7^(-s))). - Amiram Eldar, Dec 27 2022

MATHEMATICA