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 A331629 #20 Dec 29 2024 04:09:09
%S A331629 130,154,170,182,232,250,290,434,484,848,944,950,988,1196,1210,1274,
%T A331629 1276,1450,1521,1564,1666,1892,1924,2618,2848,2888,2926,3094,3232,
%U A331629 3424,3458,3542,3616,4186,4214,4250,4522,4750,4810,5150,5278,5330,5510,5590,5642,5890
%N A331629 Integers that are exactly 3-deficient-perfect numbers.
%C A331629 Aursukaree & Pongsriiam prove that 1521 is the only odd term with at most two distinct prime factors.
%C A331629 Numbers k that have 3 distinct proper divisors, d_1, d_2 and d_3, such that sigma(k) = 2*k - (d_1 + d_2 + d_3). - _Amiram Eldar_, Dec 29 2024
%H A331629 Amiram Eldar, <a href="/A331629/b331629.txt">Table of n, a(n) for n = 1..1000</a>
%H A331629 Saralee Aursukaree and Prapanpong Pongsriiam, <a href="https://arxiv.org/abs/2001.06953">On Exactly 3-Deficient-Perfect Numbers</a>, arXiv:2001.06953 [math.NT], 2020.
%e A331629 130 is an exactly 3-deficient-perfect number with d1=1, d2=2 and d3=5: sigma(130) = 252 = 2*130 - (1+2+5).
%t A331629 def3[n_] := Catch@ Block[{s = 2*n - DivisorSigma[1, n], d}, If[s > 0, d = Most@ Divisors@ n; Do[If[s == d[[i]] + d[[j]] + d[[k]], Throw@ True], {i, 3, Length@ d}, {j, i-1}, {k, j-1}]; False]]; Select[ Range[6000], def3] (* _Giovanni Resta_, Jan 23 2020 *)
%Y A331629 Cf. A000203 (sigma), A271816 (deficient-perfect numbers (k=1)), A331627 (k-deficient-perfect), A331628 (2-deficient-perfect).
%K A331629 nonn
%O A331629 1,1
%A A331629 _Michel Marcus_, Jan 23 2020
%E A331629 More terms from _Giovanni Resta_, Jan 23 2020