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A063718 a(n) is the smallest divisor of n^2 that is greater than n. 3
4, 9, 8, 25, 9, 49, 16, 27, 20, 121, 16, 169, 28, 25, 32, 289, 27, 361, 25, 49, 44, 529, 32, 125, 52, 81, 49, 841, 36, 961, 64, 99, 68, 49, 48, 1369, 76, 117, 50, 1681, 49, 1849, 88, 75, 92, 2209, 64, 343, 100, 153, 104, 2809, 81, 121, 64, 171, 116, 3481, 72, 3721, 124 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

COMMENTS

Larger of two distinct numbers with minimum sum whose geometric mean is n. E.g., a(12) = 16 as 12^2 = 144 = 1*144 = 2*72 = 3*48 = 4*36 = 6*24 = 8*18 = 9*16, etc. - Amarnath Murthy, Feb 15 2003

LINKS

Harry J. Smith, Table of n, a(n) for n = 2..1000

EXAMPLE

a(45)=75 because divisors of 45^2 are {1, 3, 5, 9, 15, 25, 27, 45, 75, 81, 135, 225, 405, 675, 2025} and the smallest element greater than 45 is 75.

MAPLE

with(numtheory): for n from 2 to 200 do a := divisors(n^2): b := a[(tau(n^2)-1)/2]: printf(`%d, `, n^2/b); od:

MATHEMATICA

sdgn[n_]:=Select[Divisors[n^2], #>n&, 1]; Flatten[Array[sdgn, 70]] (* Harvey P. Dale, Jun 18 2012 *)

PROG

(PARI) { for (n=2, 1000, d=divisors(n^2); write("b063718.txt", n, " ", d[2 + length(d)\2]) ) } \\ Harry J. Smith, Aug 28 2009

CROSSREFS

A063648(n) = n + a(n), A063717(n) = n^2/A063718(n), A063427(n) = n - a(n).

Cf. A063717.

Sequence in context: A140580 A289280 A077662 * A063748 A121920 A318279

Adjacent sequences:  A063715 A063716 A063717 * A063719 A063720 A063721

KEYWORD

nonn

AUTHOR

Vladeta Jovovic, Aug 12 2001

STATUS

approved

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Last modified April 22 10:29 EDT 2019. Contains 322330 sequences. (Running on oeis4.)