login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A158975 a(n) = sum of numbers k <= n such that all proper divisors of k are divisors of n. 1
1, 3, 6, 10, 11, 21, 18, 30, 27, 32, 29, 68, 42, 60, 66, 70, 59, 96, 78, 120, 108, 104, 101, 180, 126, 131, 137, 155, 130, 229, 161, 221, 203, 199, 221, 281, 198, 240, 246, 321, 239, 335, 282, 360, 403, 332, 329, 488, 378, 418, 389, 419, 382, 500, 462, 557, 448 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
For primes p, a(p) = A158662(p) = A014284(A036234(p)).
LINKS
EXAMPLE
For n = 8 we have the following proper divisors of k <= n: {1}, {1}, {1}, {1, 2}, {1}, {1, 2, 3}, {1}, {1, 2, 4}. Only k = 6 has a proper divisor that is not a divisor of 8, viz. 3. Hence a(8) = 1 + 2 + 3 + 4 + 5 + 7 + 8 = 30.
PROG
(Magma) [ &+[ k: k in [1..n] | forall(t){ d: d in Divisors(k) | d eq k or d in Divisors(n) } ]: n in [1..57] ];
CROSSREFS
Cf. A000040, A158662, A014284, A036234, 158973.
Sequence in context: A183545 A351827 A351828 * A282876 A363775 A261662
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Apr 01 2009
EXTENSIONS
Edited and extended by Klaus Brockhaus, Apr 06 2009
STATUS
approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 24 21:31 EDT 2024. Contains 374585 sequences. (Running on oeis4.)