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 A351827 #7 Dec 31 2023 18:47:55
%S A351827 1,3,6,10,11,17,18,30,27,28,29,51,42,56,57,70,59,92,78,112,99,100,101,
%T A351827 155,126,127,137,147,130,191,161,221,194,195,196,246,198,236,237,280,
%U A351827 239,322,282,352,351,328,329,447,378,414,380,411,382,496,437,492,439,440,441,598
%N A351827 Sum of the numbers <= n that are either prime, a divisor of n, or both.
%F A351827 a(n) = Sum_{k=1..n} k * (u(k) + v(n/k) - u(k)*v(n/k)), where u(n) is the prime characteristic (A010051) and v(n) = 1 - ceiling(n) + floor(n).
%F A351827 a(n) = sigma(n) - sopf(n) + Sum_{p<=n, p prime} p. - _Wesley Ivan Hurt_, Dec 31 2023
%Y A351827 Cf. A000203 (sigma), A008472 (sopf), A010051, A034387, A351519.
%K A351827 nonn
%O A351827 1,2
%A A351827 _Wesley Ivan Hurt_, Feb 20 2022