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 A161643 #7 Oct 07 2024 01:06:19 %S A161643 2,5,2,3,14,5,27,12,2,5,14,25,65,5,5,90,3,27,14,2,63,152,18,5,189,88, %T A161643 14,27,65,12,275,5,7,14,150,90,5,56,27,187,434,14,495,25,2,81,65,152, %U A161643 273,27,5,702,12,189,45,90,14,3,860,27,143,945,432,65,14,70,275,493,1127,180,5,27 %N A161643 Sum of all numbers from the smallest up to the largest prime factor of the n-th composite. %F A161643 a(n) = A000217(A052369(n))-A000217(A056608(n)-1). - _R. J. Mathar_, Jun 16 2009 %e A161643 For n = 5, the 5th composite is 10 = 2*5. a(5) = 2+3+4+5 = 14. %Y A161643 Cf. A002808. %K A161643 nonn,less %O A161643 1,1 %A A161643 _Juri-Stepan Gerasimov_, Jun 15 2009 %E A161643 Replaced 80 by 90 in two places, _R. J. Mathar_, Jun 16 2009