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Numbers k such that k*(k+2) gives the concatenation of two numbers m and m-1.
4

%I #9 Jul 18 2021 02:56:58

%S 36363636363,45454545454,54545454545,63636363636,72727272727,

%T 81818181818,90909090909,428571428571428571428,571428571428571428571,

%U 714285714285714285714,857142857142857142857

%N Numbers k such that k*(k+2) gives the concatenation of two numbers m and m-1.

%e 36363636363 * 36363636365 = 13223140496//13223140495, where // denotes concatenation.

%Y Cf. A102567, A116273, A116280, A116286.

%K nonn,base

%O 1,1

%A _Giovanni Resta_, Feb 06 2006