|
Search: id:A125843
|
|
|
| A125843 |
|
a(1)=1. a(n) = the sum of the terms from among the first floor(n/2) terms of the sequence which are coprime to n. |
|
+0
2
|
|
| 1, 1, 1, 2, 2, 3, 3, 3, 5, 3, 7, 3, 10, 9, 7, 12, 16, 8, 21, 15, 12, 27, 31, 15, 29, 30, 29, 32, 53, 17, 60, 46, 36, 46, 59, 22, 96, 67, 60, 62, 132, 8, 144, 109, 45, 140, 202, 53, 182, 149, 120, 184, 276, 111, 230, 178, 181, 208, 390, 176, 407, 252, 237, 283, 378, 181
(list; graph; listen)
|
|
|
OFFSET
|
1,4
|
|
|
EXAMPLE
|
The first floor(15/2) terms of the sequence are 1,1,1,2,2,3,3. Of these, five terms (1,1,1,2,2) are coprime to 15. So a(15) = 1+1+1+2+2 = 7.
|
|
MATHEMATICA
|
f[l_List] := Block[{n = Length[l] + 1}, Append[l, Plus @@ Select[Take[l, Floor[n/2]], GCD[ #, n] == 1 &]]]; Nest[f, {1}, 65] (*Chandler*)
|
|
CROSSREFS
|
Cf. A125842.
Sequence in context: A110876 A136132 A136545 this_sequence A127332 A087826 A131624
Adjacent sequences: A125840 A125841 A125842 this_sequence A125844 A125845 A125846
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Leroy Quet (qq-quet(AT)mindspring.com), Dec 10 2006
|
|
EXTENSIONS
|
Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Dec 11 2006
|
|
|
Search completed in 0.002 seconds
|
