%I #9 Jan 28 2024 04:50:29

%S 378,617,708,903,8761,45456,54539,693063,8181812,88235288,327935224,

%T 330669332,363636365,418318517,428571430,461538455,538461540,

%U 571428565,581681478,636363630,669330663,672064771,691571588

%N k times k+6 gives the concatenation of two numbers m and m+7.

%H Robert Israel, <a href="/A116339/b116339.txt">Table of n, a(n) for n = 1..8987</a>

%p f:= proc(d) local S,x;

%p S:= map(rhs@op,[msolve((x+3)^2 = 16, 10^d+1)]);

%p end proc:

%p g:= proc(n,d) local m; m:= ((n+3)^2-16)/(10^d+1)+7; m >= 10^(d-1) and m < 10^d end proc:

%p sort([seq](op(select(g,f(i),i)),i=2..13)); # _Robert Israel_, Jan 27 2024

%Y Cf. A116208, A116325, A116338, A116340, A116345.

%K nonn,base

%O 1,1

%A _Giovanni Resta_, Feb 06 2006