A088433 Number of ways to write n as n = u*v*w with 1<=u<=v<w.

0, 1, 1, 1, 1, 2, 1, 2, 1, 2, 1, 4, 1, 2, 2, 3, 1, 3, 1, 4, 2, 2, 1, 6, 1, 2, 2, 4, 1, 5, 1, 4, 2, 2, 2, 7, 1, 2, 2, 6, 1, 5, 1, 4, 4, 2, 1, 8, 1, 3, 2, 4, 1, 6, 2, 6, 2, 2, 1, 10, 1, 2, 4, 5, 2, 5, 1, 4, 2, 5, 1, 11, 1, 2, 3, 4, 2, 5, 1, 9, 3, 2, 1, 10, 2, 2, 2, 6, 1, 10, 2, 4, 2, 2, 2, 12, 1, 3, 4, 6

Offset

1,6

Comments

a(n) = 1 iff n prime or n prime^2: a(A000430(n))=1.

Links

Antti Karttunen, Table of n, a(n) for n = 1..2048

Example

n=12: (1,1,12), (1,2,6), (1,3,4), (2,2,3): therefore a(12)=4;
n=18: (1,1,18), (1,2,9), (1,3,6): therefore a(18)=3.

Prog

(PARI) A088433(n) = { my(s=0); fordiv(n, u, for(v=u, n-1, for(w=v+1, n, if(u*v*w==n, s++)))); (s); }; \\ Antti Karttunen, Aug 24 2017

Crossrefs

Cf. A034836, A088432, A088434, A122179, A122180.

Sequence in context: A354060 A194448 A238950 * A335434 A348379 A264440

Adjacent sequences: A088430 A088431 A088432 * A088434 A088435 A088436

Keyword

nonn

Author

Reinhard Zumkeller, Oct 01 2003

Status

approved