A274094 a(0)=0; thereafter (-1)^(n+1)*n appears n times.

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, 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, -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

Offset: 0

Author

N. J. A. Sloane, Jun 10 2016

Keywords

• sign

Links

• Chai Wah Wu, Table of n, a(n) for n = 0..10011

Crossrefs

Cf. A002024, A274093.

Partial sums of A010816.

Programs

Maple

s1:=[0];
for n from 1 to 15 do
for i from 1 to n do
s1:=[op(s1),(-1)^(n+1)*n]; od: od:
s1;

Mathematica

Join[{0}, Flatten[Table[(-1)^(n+1)*n, {n, 15}, {n}]]] (* Paolo Xausa, Sep 30 2024 *)
Join[{0},Flatten[Table[PadRight[{},n,(-1)^(n+1) n],{n,15}]]] (* Harvey P. Dale, Nov 28 2024 *)

Python

A274094_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

Python

from math import isqrt
def A274094(n): return m if (m:=isqrt(n<<3)+1>>1)&1 else -m # Chai Wah Wu, Nov 05 2024