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 A206025 #16 Aug 08 2024 06:41:55 %S A206025 120,780,2016,3240,4560,5460,7140,7260,9180,10296,10440,12720,19110, %T A206025 21528,23220,26796,28680,28920,32640,34980,37128,39060,41328,49770, %U A206025 51360,56280,61776,64620,64980,73920,79800,97020,100128,103740,107880,114960,115440,122760 %N A206025 Triangular numbers k whose divisors can be partitioned into three disjoint sets whose sums are all sigma(k)/3. %C A206025 Divisors of triangular number k = 120 can be partitioned into three disjoint sets whose sums are all sigma(k)/3 and this value is triangular numbers (=120). Are there other such triangular numbers? %H A206025 Amiram Eldar, <a href="/A206025/b206025.txt">Table of n, a(n) for n = 1..398</a> %e A206025 Triangular number 780 is in sequence because sigma(780)/3 = 784 = 4+780 = 2+5+6+10+12+13+15+20+26+30+39+52+60+65+78+156+195 = 1+3+130+260+390 (summands are all divisors of 780). %Y A206025 Intersection of A000217 and A204830. %Y A206025 Subsequence of A023197. %Y A206025 Cf. A000203. %K A206025 nonn %O A206025 1,1 %A A206025 _Jaroslav Krizek_, Feb 03 2012