A232655 - OEIS

%I #7 Nov 28 2013 15:42:36

%S 5,13,19,103,139,181,193,271,277,313,379,433,577,619,631,853,859,883,

%T 1093,1117,1123,1237,1279,1321,1741,1873,1933,1987,2659,2707,2713,

%U 2719,2767,2791,3163,3217,3271,3331,3469,3529,3547,3631,3637,3727,3907,3943,4129,4177

%N Primes p such that reversal (p^2+p) is also prime.

%H K. D. Bajpai, <a href="/A232655/b232655.txt">Table of n, a(n) for n = 1..6650</a>

%e a(2)= 13, it is prime: n= 6, prime(6)= 13: reversal(13^2+13)= 281, which is also prime.

%e a(4)= 103, it is prime: n= 27, prime(27)= 103: reversal(103^2+103)= 21701, which is also prime.

%e a(6)= 181, it is prime: n= 42, prime(42)= 181: reversal(181^2+181)= 24923, which is also prime.

%p with(StringTools): KD:= proc() local a, p; p:=ithprime(n); a:= parse(Reverse(convert((p^2+p), string))); if isprime(a) then RETURN (p): fi; end: seq(KD(), n=1..3000);

%t Select[Prime[Range[3000]], PrimeQ[FromDigits[Reverse[IntegerDigits[#^2 + #]]]] &]

%Y Cf. A004087 (primes written backwards).

%Y Cf. A061783 (primes p: p+(p reversed)is also prime).

%Y Cf. A232446 (primes p: reversal(p^2)+p is also prime).

%K nonn,base,less

%O 1,1

%A _K. D. Bajpai_, Nov 27 2013