A089702 - OEIS

%I #6 Aug 13 2017 21:43:44

%S 2,3,3,3,3,23,43,59,67,83,199,239,421,569,613,1307,2017,2129,2467,

%T 2741,2953,3011,3319,3413,3607,3617,5449,6917,7333,7529,8389,10211,

%U 10357,12641,12703,15077,17107,21341,21799,22469,32911,33587,33613,33647

%N a(1) = 2 then primes in nondecreasing order such that every concatenation is prime.

%e 2,23,233,2333,23333,2333323 etc. are primes.

%p ds:=proc(s) local j: RETURN(add(s[j]*10^(j-1),j=1..nops(s))):end: a:=[2]: k:=1: for n from 1 to 50 do l:=nops(a): for i from k do p:=ithprime(i): if isprime(ds([op(convert(p,base,10)),seq(op(convert(a[l-j],base,10)),j=0..l-1)])) then a:=[op(a),p]: k:=i: break fi od od: op(a); # C. Ronaldo

%Y Cf. A089703.

%K base,nonn

%O 0,1

%A _Amarnath Murthy_, Nov 10 2003

%E More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Dec 25 2004