login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A145915 Even composites in A145832. 1
146, 164, 458, 524, 584, 626, 764, 956, 1084, 1172, 1322, 1478, 1858, 1934, 2138, 2174, 2336, 2966, 3158, 3464, 3548, 3566, 3884, 3974, 3998, 4124, 4274, 4346, 4696, 5042, 5102, 5246, 5354, 5414, 6002, 6038, 6434, 6626, 6646, 6782, 6884, 7034, 7094 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A145832 is the sequence of numbers n such that for each divisor d of n, k = d + n/d is square-root smooth, i.e. p <= sqrt(k), where p is the largest prime dividing k.

LINKS

Table of n, a(n) for n=1..43.

Eric Weisstein's World of Mathematics, Round Number

EXAMPLE

146 = 2*73 is even and composite, 1, 2, 73, 146 are its divisors. 1+146/1 = 146+146/146 = 147 = 3*7^2 and 7 < 12 < sqrt(147); 2+146/2 = 73+146/73 = 75 = 3*5^2 and 5 < 8 < sqrt(75). Hence 146 is in the sequence.

PROG

(MAGMA) [ n: n in [4..7100 by 2] | forall{ k: k in [ Integers()!(d+n/d): d in [ D[j]: j in [1..a] ] ] | k ge (IsEmpty(T) select 1 else Max(T) where T is [ x[1]: x in Factorization(k) ])^2 } where a is IsOdd(#D) select (#D+1)/2 else #D/2 where D is Divisors(n) ];

CROSSREFS

Cf. A145832, A048098 (square-root smooth numbers), A145916.

Sequence in context: A124969 A294594 A031510 * A248406 A135666 A119379

Adjacent sequences:  A145912 A145913 A145914 * A145916 A145917 A145918

KEYWORD

nonn

AUTHOR

Klaus Brockhaus, Oct 26 2008

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 8 01:33 EDT 2020. Contains 336283 sequences. (Running on oeis4.)