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 A108406 #14 Mar 05 2024 14:42:28 %S A108406 0,211,220,235,20403,111416,1011231,3444142,10003400,22303600, %T A108406 31151021,53231032,121542025,126423126,202032110,243425212,302434003, %U A108406 311544033,324231521,334130241,375607602,406221650,561620561,662033363,1053045074 %N A108406 Numbers k such that concatenating k and the sum of the digits of k raised to their own power (A045503) produces a square. %e A108406 235 is a term because 2^2 + 3^3 + 5^5 = 3156 and 2353156 = 1534^2. %o A108406 (PARI) f(n)=if(n, n=digits(n); sum(i=1, #n, n[i]^n[i]), 1); \\ A045503 %o A108406 isok(k) = issquare(fromdigits(concat(digits(k), digits(f(k))))); \\ _Michel Marcus_, Mar 05 2024 %Y A108406 Cf. A045503, A108302. %K A108406 base,nonn %O A108406 1,2 %A A108406 _Jason Earls_, Jul 04 2005 %E A108406 More terms from _Ryan Propper_, Jul 07 2005