A112749 - OEIS

%I #12 Dec 14 2023 14:23:48

%S 53,577,5333,59999,511111,5111111111111,59999999,577777777,

%T 5171717171717171717,59999999999,52727272727272727272727,

%U 5111111111111,53333333333333,577777777777777,5111111111111111

%N Smallest prime of the form 5 followed by n copies of some k.

%H Robert Israel, <a href="/A112749/b112749.txt">Table of n, a(n) for n = 1..249</a>

%e a(3) = 5333, 5 followed by three copies of 3.

%p cat3 := proc(a,b,n) local resu,i ; resu := a ; for i from 1 to n do resu := resu*10^( max(1,ilog10(b)+1) )+b ; od: RETURN(resu) ; end: A112749 := proc(n) local a,k; for k from 1 do a := cat3(5,k,n) ; if isprime(a) then RETURN(a) ; fi ; od: end: seq(A112749(n),n=1..20) ; # _R. J. Mathar_, Feb 08 2008

%K base,nonn

%O 1,1

%A _Amarnath Murthy_, Jan 02 2006

%E More terms from _R. J. Mathar_, Feb 08 2008