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Numbers k such that the concatenation of k with k+5 gives a square.
19

%I #8 Jul 15 2021 06:19:02

%S 1,4,20,31,14564,38239,69919,120395,426436,902596,7478020,9090220,

%T 6671332084,8114264059,8482227259,9900250996,2244338786836,

%U 2490577152964,2509440638591,2769448208395,7012067592220

%N Numbers k such that the concatenation of k with k+5 gives a square.

%C Also numbers k such that k concatenated with k+1 gives the product of two numbers which differ by 4.

%C Also numbers k such that k concatenated with k+4 gives the product of two numbers which differ by 2.

%e 14564_14569 = 38163^2.

%Y Cf. A030465, A102567, A115426, A115437, A115429, A115430, A115431, A115432, A115433, A115434, A115435, A115436, A115439.

%Y Cf. A116125, A116099, A116167, A116297, A116177, A116171, A116185, A116315.

%K nonn,base

%O 1,2

%A _Giovanni Resta_, Feb 06 2006

%E Edited by _N. J. A. Sloane_, Apr 13 2007