A134803 Numbers n such that the sum of all numbers of the same parity <= n is equal to the sum of numbers of the opposite parity from n+1 to n+m, where m is odd and > 1.

3, 8, 119, 288, 4059, 9800

Offset: 1

Author

Paolo P. Lava and Giorgio Balzarotti, Jan 28 2008

Keywords

• easy
• nonn

Examples

			3 -> 1+3 = 4 = 4
8 -> 2+4+6+8 = 20 = 9+11
119 -> 1+3+5+...+119 = 3600 = 120+122+...+168
		

Crossrefs

Cf. A001109, A084068, A089895.

Programs

Maple

P:=proc(n) local a,k,i,s1,s2; for i from 1 by 1 to n do if 2*trunc(i/2)=i then s1:=sum('2*k','k'=1..(i/2)); else s1:=sum('2*k-1','k'=1..(i+1)/2); fi; a:=1; s2:=i+1; while s1>s2 do a:=a+2; s2:=s2+i+a; od; if s1=s2 then lprint(i,s1); fi; od; end: P(10000);