A108406 Numbers k such that concatenating k and the sum of the digits of k raised to their own power (A045503) produces a square.
0, 211, 220, 235, 20403, 111416, 1011231, 3444142, 10003400, 22303600, 31151021, 53231032, 121542025, 126423126, 202032110, 243425212, 302434003, 311544033, 324231521, 334130241, 375607602, 406221650, 561620561, 662033363, 1053045074
Offset: 1
Examples
235 is a term because 2^2 + 3^3 + 5^5 = 3156 and 2353156 = 1534^2.
Programs
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PARI
f(n)=if(n, n=digits(n); sum(i=1, #n, n[i]^n[i]), 1); \\ A045503 isok(k) = issquare(fromdigits(concat(digits(k), digits(f(k))))); \\ Michel Marcus, Mar 05 2024
Extensions
More terms from Ryan Propper, Jul 07 2005