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Smallest prime beginning with the concatenation of first n primes.
1

%I #7 Aug 09 2015 00:20:47

%S 2,23,2351,2357,2357119,2357111357,23571113171,23571113171939,

%T 2357111317192343,23571113171923297,2357111317192329319,

%U 235711131719232931373,235711131719232931374149

%N Smallest prime beginning with the concatenation of first n primes.

%F a(n) >= A019518(n). - _R. J. Mathar_, Jan 25 2008

%e a(5) = 2357119 as 2357111,2357113,2357117 are composite.

%p A055642 := proc(n) max(1,ilog10(n)+1) ; end: glue := proc(a,b) a*10^A055642(b)+b ; end: A019518 := proc(n) local a,j,p ; a := 2; for j from 2 to n do p := ithprime(j) ; a := glue(a,p) ; od: RETURN(a) ; end: A114794 := proc(n) local b,j ; b := A019518(n) ; if isprime(b) then RETURN(b) ; else for j from 1 do if isprime(glue(b,j)) then RETURN( glue(b,j) ) ; fi ; od: fi ; end: seq(A114794(n),n=1..20) ; # _R. J. Mathar_, Jan 25 2008

%K base,nonn

%O 1,1

%A _Amarnath Murthy_, Nov 19 2005

%E More terms from _R. J. Mathar_, Jan 25 2008