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 A243971 #18 Jul 22 2017 20:49:22 %S A243971 1,2,5,10,16,19,26,29,34,37,43,46,58,64,65,67,73,82,86,94,101,109,122, %T A243971 130,134,142,145,146,149,157,163,190,193,197,199,202,206,211,229,257, %U A243971 262,281,283,290,298,302,310,334,337,347,349,367,401,409,421,430 %N A243971 Numbers n that cannot be obtained as a partial sum of the divisors (taken in descending order, from m down to 1) of any m < n. %C A243971 Numbers such that A243970(n) = n. %C A243971 Is this sequence infinite? - _Franklin T. Adams-Watters_, Jul 20 2017 %H A243971 Alois P. Heinz, <a href="/A243971/b243971.txt">Table of n, a(n) for n = 1..10000</a> %e A243971 From n=1 to 4, these partial sums are: 1; 2, 3; 3, 4; 4, 6, 7. So it is not possible to obtain 5 with any partial sum of divisors of numbers that are less than 5. And indeed A243970(5) is equal to 5. Hence 5 is in this sequence. %t A243971 Module[{nn = 432, s}, s = Array[Function[d, Array[Total@ Take[d, -#] &, Length@ d]]@ Divisors@ # &, nn - 1]; Select[Range@ nn, ! MemberQ[Flatten@ Take[s, # - 1], #] &]] (* _Michael De Vlieger_, Jul 22 2017 *) %Y A243971 Cf. A243970. %K A243971 nonn %O A243971 1,2 %A A243971 _Michel Marcus_, Jun 16 2014