A104076 - OEIS

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A104076

If k(m) is the m-th divisor (when the divisors are ordered by size) of n, then a(n) = gcd(k(1)+k(2), k(2)+k(3), k(3)+k(4), ..., k(j-1)+k(j)), where j is the number of divisors of n.

3, 4, 3, 6, 1, 8, 3, 4, 1, 12, 1, 14, 3, 4, 3, 18, 1, 20, 3, 2, 1, 24, 1, 6, 3, 4, 1, 30, 1, 32, 3, 2, 1, 6, 1, 38, 3, 4, 1, 42, 1, 44, 3, 2, 1, 48, 1, 8, 1, 4, 1, 54, 1, 2, 1, 2, 1, 60, 1, 62, 3, 2, 3, 6, 1, 68, 3, 2, 1, 72, 1, 74, 3, 4, 1, 2, 1, 80, 1, 4, 1, 84, 1, 2, 3, 4, 1, 90, 1, 4, 3, 2, 1, 6, 1, 98

(list; graph; refs; listen; history; text; internal format)

OFFSET

2,1

LINKS

Harvey P. Dale, Table of n, a(n) for n = 2..1000

EXAMPLE

The divisors of 14 are 1,2,7,14. So a(14) = gcd(1+2, 2+7, 7+14) = 3.

MAPLE

A104076 := proc(n) local dvs ; dvs := sort(convert(numtheory[divisors](n), list)) ; igcd(seq( op(i, dvs)+op(i+1, dvs), i=1..nops(dvs)-1)) ; end: for n from 2 to 140 do printf("%d, ", A104076(n)) ; od: # R. J. Mathar, Sep 05 2008

MATHEMATICA

Table[GCD@@(Total/@Partition[Divisors[n], 2, 1]), {n, 2, 100}] (* Harvey P. Dale, Dec 18 2018 *)

CROSSREFS

Cf. A143771.

Sequence in context: A360059 A262150 A325594 * A238161 A332880 A281626

Adjacent sequences: A104073 A104074 A104075 * A104077 A104078 A104079

KEYWORD

nonn

AUTHOR

Leroy Quet, Aug 31 2008

EXTENSIONS

Extended by R. J. Mathar, Sep 05 2008

Definition corrected by Leroy Quet, Sep 21 2008

STATUS

approved