This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A070555 #8 Oct 19 2019 23:44:50 %S A070555 1,1,6,15,12,45,66,21,120,153,50,231,180,117,378,435,144,255,630,209, %T A070555 780,861,198,1035,840,375,1326,729,476,1653,1770,465,1056,2145,714, %U A070555 2415,2556,555,1710,3003,1080,3321,1890,1161,3828,2475,1334,2397,4560,1323 %N A070555 Sum of positive integers k, where k <= n and gcd(k,2n+1) = gcd(k+1,2n+1). %C A070555 Note that whenever gcd(k,2n+1) = gcd(k+1,2n+1), this common value must be 1. - _David Wasserman_, May 13 2003 %o A070555 (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 A070555 Bisection of A069828. %K A070555 nonn %O A070555 1,3 %A A070555 _Vladeta Jovovic_, Apr 29 2002 %E A070555 More terms from _David Wasserman_, May 13 2003