A252005 - OEIS

%I #16 Sep 30 2018 17:46:11

%S 2,3,11,23,53,83,101,113,149,179,239,269,293,311,347,359,383,401,419,

%T 449,479,557,563,593,617,647,653,683,743,773,839,863,929,953,983,1019,

%U 1061,1091,1151,1163,1223,1301,1319,1367,1373,1439,1481,1493,1553,1583,1607,1619,1667,1697,1733,1787,1823

%N a(1)=2; for n>1, a(n) is the least prime > a(n-1) such that sum of digits of a(n-1) and a(n) is prime.

%H Zak Seidov, <a href="/A252005/b252005.txt">Table of n, a(n) for n = 1..1000</a>

%e a(2)=3, next primes are 5, 7, 11 and only 3+1+1 is prime, hence

%e a(3)=11, next primes are 13, 17, 19, 23 and only 1+1+2+3 is prime, hence a(4)=23, etc.

%t lp[n_]:=Module[{p=NextPrime[n],tid=Total[IntegerDigits[n]]}, While[ CompositeQ[ Total[ IntegerDigits[p]]+tid],p=NextPrime[p]];p]; NestList[ lp,2,60] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Sep 30 2018 *)

%Y Cf. A007953, A252006.

%K base,nonn

%O 1,1

%A _Zak Seidov_, Dec 12 2014