login
a(0)=0; thereafter (-1)^n*n appears n times.
2

%I #17 Nov 05 2024 12:18:56

%S 0,-1,2,2,-3,-3,-3,4,4,4,4,-5,-5,-5,-5,-5,6,6,6,6,6,6,-7,-7,-7,-7,-7,

%T -7,-7,8,8,8,8,8,8,8,8,-9,-9,-9,-9,-9,-9,-9,-9,-9,10,10,10,10,10,10,

%U 10,10,10,10,-11,-11,-11,-11,-11,-11,-11,-11,-11,-11,-11,12,12,12,12,12,12,12,12,12,12,12

%N a(0)=0; thereafter (-1)^n*n appears n times.

%H Chai Wah Wu, <a href="/A274093/b274093.txt">Table of n, a(n) for n = 0..10011</a>

%p s1:=[0];

%p for n from 1 to 15 do

%p for i from 1 to n do

%p s1:=[op(s1),(-1)^n*n]; od: od:

%p s1;

%t Join[{0}, Flatten[Table[(-1)^n*n, {n, 15}, {n}]]] (* _Paolo Xausa_, Sep 30 2024 *)

%o (Python)

%o A274093_list = [0]+ [i for n in range(1,142) for i in [-n if n % 2 else n]*n] # _Chai Wah Wu_, Jun 11 2016

%o (Python)

%o from math import isqrt

%o def A274093(n): return -m if (m:=isqrt(n<<3)+1>>1)&1 else m # _Chai Wah Wu_, Nov 05 2024

%Y Cf. A002024, A274094.

%K sign,changed

%O 0,3

%A _N. J. A. Sloane_, Jun 10 2016