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Sum of positive integers k, where k <= n and gcd(k,2n+1) = gcd(k+1,2n+1).
2

%I #8 Oct 19 2019 23:44:50

%S 1,1,6,15,12,45,66,21,120,153,50,231,180,117,378,435,144,255,630,209,

%T 780,861,198,1035,840,375,1326,729,476,1653,1770,465,1056,2145,714,

%U 2415,2556,555,1710,3003,1080,3321,1890,1161,3828,2475,1334,2397,4560,1323

%N Sum of positive integers k, where k <= n and gcd(k,2n+1) = gcd(k+1,2n+1).

%C Note that whenever gcd(k,2n+1) = gcd(k+1,2n+1), this common value must be 1. - _David Wasserman_, May 13 2003

%o (MATLAB) function m = A070555(n) m = 0; for k = 1:(2*n + 1) if gcd(k, 2*n + 1) == gcd(k + 1, 2*n + 1) m = m + k; end end

%Y Bisection of A069828.

%K nonn

%O 1,3

%A _Vladeta Jovovic_, Apr 29 2002

%E More terms from _David Wasserman_, May 13 2003