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 A345261 #10 May 15 2025 19:15:04
%S A345261 1,5,10,13,26,50,50,29,37,130,122,130,170,250,260,61,290,185,362,338,
%T A345261 500,610,530,290,151,850,118,650,842,1300,962,125,1220,1450,1300,481,
%U A345261 1370,1810,1700,754,1682,2500,1850,1586,962,2650,2210,610,393,755,2900,2210,2810,590
%N A345261 a(n) = Sum_{d|n} d * rad(d).
%C A345261 If p is prime, a(p) = Sum_{p|d} d * rad(d) = 1*1 + p*p = p^2 + 1.
%C A345261 Inverse Möbius transform of n * rad(n). - _Wesley Ivan Hurt_, Mar 31 2025
%F A345261 a(prime(n)) = A066872(n). - _Michel Marcus_, Jun 12 2021
%e A345261 a(10) = Sum_{d|10} d * rad(d) = 1*1 + 2*2 + 5*5 + 10*10 = 1 + 4 + 25 + 100 = 130.
%t A345261 Table[Sum[i (1 - Ceiling[n/i] + Floor[n/i]) Product[k^((PrimePi[k] - PrimePi[k - 1]) (1 - Ceiling[i/k] + Floor[i/k])), {k, i}], {i, n}], {n, 80}]
%o A345261 (PARI) rad(n) = factorback(factorint(n)[, 1]);
%o A345261 a(n) = sumdiv(n, d, d*rad(d)); \\ _Michel Marcus_, Jun 12 2021
%Y A345261 Cf. A007947 (rad), A066872, A345263.
%K A345261 nonn
%O A345261 1,2
%A A345261 _Wesley Ivan Hurt_, Jun 12 2021