|
| |
|
|
A051278
|
|
n=k/d(k) has a unique solution, where d(k) = number of divisors of k.
|
|
9
| |
|
|
4, 6, 9, 10, 12, 14, 15, 20, 21, 22, 26, 32, 33, 34, 35, 36, 38, 39, 42, 46, 50, 51, 55, 57, 58, 60, 62, 65, 66, 69, 70, 74, 75, 77, 78, 82, 85, 86, 87, 90, 91, 93, 94, 95, 96, 98, 100, 102, 106, 108, 110, 111, 114, 115, 118, 119, 122, 123, 126, 128, 129, 130
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,1
|
|
|
COMMENTS
| Because d(k) <= 2*sqrt(k), it suffices to check k from 1 to 4*n^2. - Nathaniel Johnston, May 04 2011
A051521(a(n)) = 1. - Reinhard Zumkeller, Dec 28 2011
|
|
|
LINKS
| T. D. Noe, Table of n, a(n) for n=1..1000
|
|
|
EXAMPLE
| 36 is the unique number k with k/d(k)=4.
|
|
|
MAPLE
| with(numtheory): A051278 := proc(n) local ct, k: ct:=0: for k from 1 to 4*n^2 do if(n=k/tau(k))then ct:=ct+1: fi: od: if(ct=1)then return n: else return NULL: fi: end: seq(A051278(n), n=1..40);
|
|
|
PROG
| (Haskell)
a051278 n = a051278_list !! (n-1)
a051278_list = filter ((== 1) . a051521) [1..]
-- Reinhard Zumkeller, Dec 28 2011
|
|
|
CROSSREFS
| Cf. A033950, A036763, A051279, A051280, A051346.
Sequence in context: A010447 A112082 A174896 * A175127 A174166 A171401
Adjacent sequences: A051275 A051276 A051277 * A051279 A051280 A051281
|
|
|
KEYWORD
| nonn,easy,nice
|
|
|
AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), R. K. Guy
|
| |
|
|
