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A182936 Greatest common divisor of the proper divisors of n, 0 if there are none. 4
0, 0, 0, 2, 0, 1, 0, 2, 3, 1, 0, 1, 0, 1, 1, 2, 0, 1, 0, 1, 1, 1, 0, 1, 5, 1, 3, 1, 0, 1, 0, 2, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 7, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 2, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 0, 1, 3, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

Here a proper divisor d of n is a divisor of n such that 1 < d < n.

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = 0 if n is not composite, p if n is a proper power of prime p, and 1 otherwise. - Franklin T. Adams-Watters, Mar 22 2011

MAPLE

A182936 := n -> igcd(op(numtheory[divisors](n) minus {1, n}));

seq(A182936(i), i=1..79); # Peter Luschny, Mar 22 2011

MATHEMATICA

Join[{0}, Table[GCD@@Most[Rest[Divisors[n]]], {n, 2, 110}]] (* Harvey P. Dale, May 04 2018 *)

PROG

(PARI) A182936(n) = { my(divs=divisors(n)); if(#divs<3, 0, gcd(vector(numdiv(n)-2, k, divs[k+1]))); }; \\ Antti Karttunen, Sep 23 2017

CROSSREFS

Cf. A048671.

Sequence in context: A329027 A235987 A104597 * A072662 A030010 A321297

Adjacent sequences:  A182933 A182934 A182935 * A182937 A182938 A182939

KEYWORD

nonn

AUTHOR

Peter Luschny, Mar 22 2011

EXTENSIONS

More terms from Antti Karttunen, Sep 23 2017

STATUS

approved

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Last modified February 22 05:54 EST 2020. Contains 332116 sequences. (Running on oeis4.)