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!)
A227065 The number of partitions of 2n into exactly two parts such that the smaller and larger parts are not both prime. 1
1, 1, 2, 3, 3, 5, 5, 6, 7, 8, 8, 9, 10, 12, 12, 14, 13, 14, 17, 17, 17, 19, 19, 19, 21, 23, 22, 25, 25, 24, 28, 27, 27, 32, 30, 30, 32, 33, 32, 36, 36, 34, 38, 40, 36, 42, 42, 41, 46, 44, 43, 47, 47, 46, 49, 49, 47, 52, 53, 48, 57, 57, 53, 61, 58, 57, 61, 63, 61, 63 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
COMMENTS
Complement of A045917(n).
LINKS
FORMULA
a(n) = n - A045917(n).
MAPLE
A227065 := proc(n)
n-A045917(n) ;
end proc:
seq(A227065(n), n=1..100) ; # R. J. Mathar, Jul 01 2013
MATHEMATICA
Table[n - Sum[(PrimePi[2 n - i] - PrimePi[2 n - i - 1]) (PrimePi[i] - PrimePi[i - 1]), {i, n}], {n, 100}] (* Wesley Ivan Hurt, Apr 07 2018 *)
f[n_]:=Length[Select[2 n - Prime[Range[PrimePi[n]]], PrimeQ]]; Table[n - f[n], {n, 100}] (* Vincenzo Librandi, Apr 10 2018 *)
CROSSREFS
Cf. A045917.
Sequence in context: A353714 A159237 A335599 * A010761 A320840 A161172
KEYWORD
nonn,easy
AUTHOR
Wesley Ivan Hurt, Jun 30 2013
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 March 19 04:26 EDT 2024. Contains 370952 sequences. (Running on oeis4.)