A095216 - OEIS

%I #9 Aug 08 2015 20:16:59

%S 2,1,5,11,27,81,153,91,71,183,27,67,147,219,347,99,831,109,627,329,

%T 1053,363,603,357,349,219,981,129,737,369,61,3447,849,237,1281,693,

%U 719,691,851,19,2349,2277,627,4163,3889,831,1049,3973,1557,1037,2943,1189,1851

%N Smallest prime divisor of n-th partial concatenation is prime(n).

%e Smallest prime divisor of 21511 which is a concatenation of first four terms 2,1,5 and 11 is prime(4) = 7, 21511= 7^2*439.

%p catL := proc(L) local resul,a ; resul := 0 ; for a in L do resul := resul*10^(max(1,ilog10(a)+1))+a ; od ; RETURN(resul) ; end: A020639 := proc(n) op(1,op(1,ifactors(n)[2])) ; end: A095216 := proc(nmax) local a,anext,n; a := [2] ; while nops(a) < nmax do anext := 0 ; n := nops(a)+1 ; while A020639(catL([op(a),anext])) <> ithprime(n) do anext := anext+1 ; od; a := [op(a),anext] ; od ; RETURN(a) ; end: A095216(15) ; # _R. J. Mathar_, Aug 03 2007

%K base,nonn

%O 1,1

%A _Amarnath Murthy_, Jun 10 2004

%E More terms from _R. J. Mathar_, Aug 03 2007

%E a(17)-a(53) from _Donovan Johnson_, May 13 2010