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!)
A202242 n such that the sum of digit !! of n equals the sum of d|n, 1<d<n. 0
14, 56, 28361, 119507, 191557, 287039, 691259, 750889 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
No further terms less than 10^8.
The double factorial n!! (A006882) of a positive integer n is the product of the positive integers <= n that have the same parity as n.
LINKS
EXAMPLE
56 is in the sequence because 5!! + 6!! = 15 + 48 = 63, and sum of the divisors 1< d< 56 = sigma(56) - 56 - 1 = 120 - 56 - 1 = 63.
MATHEMATICA
Q[n_]:=Module[{a=Total[Rest[Most[Divisors[n]]]]}, a == Total[IntegerDigits[n]!!]]; Select[Range[2, 10^5], Q]
CROSSREFS
Sequence in context: A281200 A212341 A067326 * A041374 A070741 A022286
KEYWORD
nonn,hard,base
AUTHOR
Michel Lagneau, Dec 16 2011
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 February 23 14:24 EST 2024. Contains 370283 sequences. (Running on oeis4.)