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 A135626 #11 Jan 15 2022 22:26:05 %S A135626 36,2296,344224,66795904,2123921902809088,55917383475391234048, %T A135626 113139095670780538912768,18936964716073275231635792697644548096, %U A135626 17844842231875188005737387074890396164121166838056340379818586412691750912 %N A135626 Product of n-th perfect number and n-th perfect number written backwards. %H A135626 Omar E. Pol, <a href="http://www.polprimos.com">Determinacion geometrica de los numeros primos y perfectos</a>. %F A135626 a(n) = A000396(n)*A135624(n). %e A135626 a(2)=2296 because the second perfect number is 28 and 28*82=2296. %t A135626 # IntegerReverse[#]&/@PerfectNumber[Range[10]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Nov 29 2020 *) %Y A135626 Cf. A000396, A133019, A135624. %K A135626 base,nonn %O A135626 1,1 %A A135626 _Omar E. Pol_, Feb 20 2008 %E A135626 More terms from _R. J. Mathar_, Jun 24 2009