A063928 Largest nonprime proper divisor of n (with a(1)=1).

1, 1, 1, 1, 1, 1, 1, 4, 1, 1, 1, 6, 1, 1, 1, 8, 1, 9, 1, 10, 1, 1, 1, 12, 1, 1, 9, 14, 1, 15, 1, 16, 1, 1, 1, 18, 1, 1, 1, 20, 1, 21, 1, 22, 15, 1, 1, 24, 1, 25, 1, 26, 1, 27, 1, 28, 1, 1, 1, 30, 1, 1, 21, 32, 1, 33, 1, 34, 1, 35, 1, 36, 1, 1, 25, 38, 1, 39, 1, 40, 27, 1, 1, 42, 1, 1, 1, 44, 1

Offset: 1

Author

Henry Bottomley, Aug 15 2001

Keywords

• nonn

Comments

a(m)*a(n) <= a(m*n); a(m)*a(n) = a(m*n) iff m and n are prime or = 1. - Reinhard Zumkeller, Apr 11 2008

Links

• R. Zumkeller, Table of n, a(n) for n = 1..1000

Crossrefs

a(n)=1 if n is 1, prime (A000040), or the product of two primes (A001358), i.e., if n is in A037143, otherwise, with n in A033942, a(n)=A032742(n). Cf. A006530.

Programs

PARI

{ for (n=1, 1000, if (n==1, a=1, d=divisors(n); m=length(d); until (!isprime(a), m--; a=d[m])); write("b063928.txt", n, " ", a) ) } \\ Harry J. Smith, Sep 02 2009