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 A329663 #12 Feb 29 2020 16:04:48 %S A329663 2,1881,49905,54585,63405,196785,853785,2094897,3925449,32480685, %T A329663 1925817945,1994453385,961201916805 %N A329663 Numbers k such that the binary reversal of k (A030101) is equal to the sum of the proper divisors of k (A001065). %C A329663 a(13) > 1.45*10^11. %C A329663 a(14) > 5*10^12, if it exists. - _Giovanni Resta_, Feb 29 2020 %e A329663 2 is a term since its binary representation is 10, its binary reversal is 01 = 1 which is equal to the sum of the proper divisors of 2. %e A329663 1881 is a term since its binary representation is 11101011001, its binary reversal is 10011010111 which is equal to 1239, which is also the sum of the proper divisors of 1881: 1 + 3 + 9 + 11 + 19 + 33 + 57 + 99 + 171 + 209 + 627 = 1239. %t A329663 Select[Range[10^5], DivisorSigma[1, #] - # == IntegerReverse[#, 2] &] %o A329663 (PARI) isok(k) = sigma(k) - k == fromdigits(Vecrev(binary(k)), 2); \\ _Michel Marcus_, Feb 29 2020 %Y A329663 Cf. A001065, A030101, A072234. %K A329663 nonn,base,more %O A329663 1,1 %A A329663 _Amiram Eldar_, Feb 28 2020 %E A329663 a(13) from _Giovanni Resta_, Feb 29 2020