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 A184390 #13 Jun 25 2022 21:54:11
%S A184390 1,3,6,36,15,666,28,2080,378,5050,66,1493856,91,19306,25425,524800,
%T A184390 153,17009028,190,32004000,97461,117370,276,55037822976,7875,228826,
%U A184390 266085,240956128,435,328050405000
%N A184390 a(n) = sum of numbers from 1 to pi(n), where pi(n) = A007955(n).
%H A184390 Harvey P. Dale, <a href="/A184390/b184390.txt">Table of n, a(n) for n = 1..1000</a>
%F A184390 a(n) = Sum_{i = 1..pi(n)} i = A000217(A007955(n)) = (1/2)*A007955(n)*(A007955(n)+1).
%e A184390 For n = 6; pi(6) = 36; a(n) = (1/2)*36*37 = 666.
%t A184390 # (#+1)/2&/@Array[Times@@Divisors[#]&,40] (* _Harvey P. Dale_, Oct 05 2012 *)
%o A184390 (Python)
%o A184390 from math import isqrt
%o A184390 from sympy import divisor_count
%o A184390 def A184390(n): return (m:=((isqrt(n) if (c:=divisor_count(n)) & 1 else 1)*n**(c//2)))*(m+1)//2 # _Chai Wah Wu_, Jun 25 2022
%Y A184390 Cf. A184387, A184388, A184389, A184391, A130674.
%K A184390 nonn
%O A184390 1,2
%A A184390 _Jaroslav Krizek_, Jan 12 2011