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 A225684 #34 Feb 16 2025 08:33:19 %S A225684 965,8150,12966911,625261742 %N A225684 Nonpalindromic numbers n with property that the sum of the reversed divisors of n is equal to n+1. %C A225684 Palindromes are excluded because palindromic primes automatically have this property, and palindromic nonprimes never have it. %C A225684 Call a number "quasi-perfect" or "slightly excessive" if sigma(n) = 2n+1 (cf. A000203). It is conjectured that no quasi-perfect number exists. The present sequence is a variation that certainly has at least four terms. %C A225684 a(5) > 10^11. - _Donovan Johnson_, May 26 2013 %C A225684 a(5) > 10^12. - _Giovanni Resta_, Aug 19 2019 %H A225684 Jason Earls, <a href="http://voices.yahoo.com/all-reversed-slightly-excessive-numbers-1315225.html">All About Reversed Slightly Excessive Numbers</a> %H A225684 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/QuasiperfectNumber.html">Quasi-perfect number</a> %e A225684 The divisors of 965 are 1, 5, 193, 965, and reversing and adding produces 1 + 5 + 391 + 569 = 966. %o A225684 (Python) %o A225684 from sympy import divisors %o A225684 def ispal(n): s = str(n); return s == s[::-1] %o A225684 def ok(n): %o A225684 return not ispal(n) and n+1 == sum(int(str(d)[::-1]) for d in divisors(n)) %o A225684 print([m for m in range(10**4) if ok(m)]) # _Michael S. Branicky_, Jan 25 2021 %Y A225684 Cf. A069192, A069250, A000203. %K A225684 nonn,base,more %O A225684 1,1 %A A225684 _N. J. A. Sloane_, May 19 2013 %E A225684 a(4) from _Donovan Johnson_, May 19 2013