The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A063928 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A063928

Largest nonprime proper divisor of n (with a(1)=1).
(history; published version)

#13 by Alois P. Heinz at Sun Jun 24 19:38:02 EDT 2018

STATUS

proposed

approved

#12 by Jon E. Schoenfield at Sun Jun 24 19:37:40 EDT 2018

STATUS

editing

proposed

#11 by Jon E. Schoenfield at Sun Jun 24 19:37:38 EDT 2018

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

PROG

(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) ) } [From _\\ _Harry J. Smith_, Sep 02 2009]

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.

STATUS

approved

editing

#10 by Russ Cox at Fri Mar 30 18:51:35 EDT 2012

AUTHOR

_Henry Bottomley (se16(AT)btinternet.com), _, Aug 15 2001

Discussion

Fri Mar 30

18:51

OEIS Server: https://oeis.org/edit/global/247

#9 by Russ Cox at Fri Mar 30 18:50:18 EDT 2012

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 (reinhard.zumkeller(AT)gmail.com), _, Apr 11 2008

Discussion

Fri Mar 30

18:50

OEIS Server: https://oeis.org/edit/global/246

#8 by Russ Cox at Fri Mar 30 17:24:25 EDT 2012

PROG

(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) ) } [From _Harry J. Smith (hjsmithh(AT)sbcglobal.net), _, Sep 02 2009]

Discussion

Fri Mar 30

17:24

OEIS Server: https://oeis.org/edit/global/133

#7 by N. J. A. Sloane at Thu Nov 11 07:34:06 EST 2010

LINKS

R. Zumkeller, <a href="/A063928/b063928.txt">Table of n, a(n) for n = 1..1000</a>

KEYWORD

nonn,new

nonn

#6 by N. J. A. Sloane at Tue Jun 01 03:00:00 EDT 2010

PROG

(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) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Sep 02 2009]

KEYWORD

nonn,new

nonn

#5 by N. J. A. Sloane at Fri Feb 27 03:00:00 EST 2009

LINKS

R. Zumkeller, <a href="http://www.research.att.com/~njas/sequences/b063928.txt">Table of n, a(n) for n = 1..1000</a>

KEYWORD

nonn,new

nonn

#4 by N. J. A. Sloane at Sun Jun 29 03:00:00 EDT 2008

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 (reinhard.zumkeller(AT)gmail.com), Apr 11 2008

LINKS

R. Zumkeller, <a href="http://www.research.att.com/~njas/sequences/b063928.txt">Table of n, a(n) for n = 1..1000</a>

KEYWORD

nonn,new

nonn