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A063721 Number of proper divisors of n is a square and sets a new record for such squares. 1
1, 2, 16, 48, 6480, 331776, 26542080, 207360000, 174142586880, 5476584960000, 8352895346933760000, 190741334440500264960000, 40745645800296001044480000, 11921333402531266560000000000000000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..14.

PROG

(PARI) a=-1; for(n=1, 10^7, x=numdiv(n)-1; if(issquare(x), b=x; if(b>a, a=b; print(n))))

(PARI) {a063721(m)=local(r, n, x); r=-1; for(n=1, m, x=numdiv(n)-1; if(issquare(x) && x>r, r=x; print1(n, ", "))) }

CROSSREFS

Cf. A032741.

Sequence in context: A162442 A159010 A223219 * A232209 A012180 A058376

Adjacent sequences: A063718 A063719 A063720 * A063722 A063723 A063724

KEYWORD

nonn

AUTHOR

Jason Earls, Aug 22 2001

EXTENSIONS

More terms from Don Reble, May 12 2002

STATUS

approved

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Last modified February 9 06:46 EST 2023. Contains 360153 sequences. (Running on oeis4.)