A167232 - OEIS

%I #11 Sep 27 2023 04:00:19

%S 1,-1,2,-2,3,-3,4,-4,5,4,4,3,4,3,5,4,7,6,10,9,14,13,19,18,25,24,32,31,

%T 40,38,38,36,37,35,37,35,38,36,40,38,43,41,47,45,52,50,58,56,65,62,62,

%U 59,60,57,59,56,59,56,60,57,62,59,65,62,69,66,74,71,80,76,76,72,73,69

%N a(n) is the number obtained by writing out numbers from 1 to n and placing an alternate + and - minus sign between successive digits and evaluating the expression written.

%H Sphere Online Judge, <a href="https://www.spoj.com/problems/KPSUM/">Problem 1433: The Sum</a>

%F a(n) = -Sum_{i=1..n} (-1)^i*A007376(i). [_R. J. Mathar_, Nov 09 2009]

%Y Cf. A007376.

%K sign,base

%O 1,3

%A Dhruv (dhruvbird(AT)gmail.com), Oct 31 2009

%E a(12) corrected, more terms appended by _R. J. Mathar_, Nov 09 2009