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%I #13 Jun 17 2017 03:56:18
%S 11,141,1441,14441,144441,1444441,14444441,144444441,1444444441,
%T 14444444441,144444444441,1444444444441,14444444444441,
%U 144444444444441,1444444444444441,14444444444444441,144444444444444441,1444444444444444441,14444444444444444441
%N a(n)=n 4's sandwiched between two 1's.
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (11,-10).
%F a(0)=11, a(n)=10*a(n-1)+31.
%F a(n) = (130*10^n-31)/9 (see PARI's code by Charles R Greathouse IV).
%t a[0]=11;a[n_]:=a[n-1]*10+31;Table[a[n],{n,0,44}]
%o (PARI) a(n)=(130*10^n-31)/9 \\ _Charles R Greathouse IV_, Jan 23 2012
%K nonn,easy,base,less
%O 0,1
%A _José María Grau Ribas_, Jan 22 2012