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 A003502 #37 Mar 10 2025 11:51:12
%S A003502 48,140,1050,1575,2024,5775,8892,9504,62744,186615,196664,199760,
%T A003502 266000,312620,526575,573560,587460,1000824,1081184,1139144,1140020,
%U A003502 1173704,1208504,1233056,1236536,1279950,1921185,2036420,2102750,2140215,2171240,2198504,2312024
%N A003502 The smaller of a betrothed pair.
%D A003502 R. K. Guy, Unsolved Problems in Number Theory, B5.
%H A003502 Giovanni Resta, <a href="/A003502/b003502.txt">Table of n, a(n) for n = 1..4122</a> (terms < 10^13, terms 1..1000 from Donovan Johnson, 1001..1126 from Amiram Eldar)
%H A003502 Shyam Sunder Gupta, <a href="https://doi.org/10.1007/978-981-97-2465-9_5">Amicable Numbers</a>, Exploring the Beauty of Fascinating Numbers, Springer (2025) Ch. 5, 159-183.
%H A003502 Peter Hagis and Graham Lord, <a href="https://doi.org/10.1090/S0025-5718-1977-0434939-3">Quasi-amicable numbers</a>, Math. Comp. 31 (1977), 608-611.
%H A003502 David Moews, <a href="http://djm.cc/augmented.fmtlist">Augmented amicable pairs</a>
%H A003502 Jan Munch Pedersen, <a href="http://62.198.248.44/aliquot/tables.htm">Tables of Aliquot Cycles</a>
%H A003502 Wikipedia, <a href="https://en.wikipedia.org/wiki/Betrothed_numbers">Betrothed numbers</a>
%e A003502 48 is a term because sigma(48) - 48 - 1 = 124 - 48 - 1 = 75 and 48 < 75 and sigma(75) - 75 - 1 = 124 - 75 - 1 = 48. - _David A. Corneth_, Jan 24 2019
%t A003502 aapQ[n_] := Module[{c=DivisorSigma[1, n]-1-n}, c!=n&&DivisorSigma[ 1, c]-1-c == n]; Transpose[Union[Sort[{#, DivisorSigma[1, #]-1-#}]&/@Select[Range[2, 10000], aapQ]]] [[1]] (* _Amiram Eldar_, Jan 24 2019 after Harvey P. Dale at A007992 *)
%o A003502 (PARI) is(n) = m = sigma(n) - n - 1; if(m == 0 || n >= m, return(0)); n == sigma(m) - m - 1 \\ _David A. Corneth_, Jan 24 2019
%Y A003502 Cf. A000203, A003503, A005276.
%K A003502 nonn,nice
%O A003502 1,1
%A A003502 _Robert G. Wilson v_
%E A003502 Computed by Fred W. Helenius (fredh(AT)ix.netcom.com)
%E A003502 Extended by _T. D. Noe_, Dec 29 2011