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Numbers k such that k^2 is the concatenation of two numbers m and 2*m.
2

%I #11 Jul 15 2021 06:27:32

%S 6,28571428571428571428572,42857142857142857142858,

%T 57142857142857142857144,

%U 2247191011235955056179775280898876404494382022471910112360

%N Numbers k such that k^2 is the concatenation of two numbers m and 2*m.

%e 6^2 = 3_6.

%Y Cf. A102567, A106497, A115527 - A115556.

%K nonn,base

%O 1,1

%A _Giovanni Resta_, Jan 25 2006