cp's OEIS Frontend

A258084 Numbers n such that n concatenated with its reversal n' yields a prime when the rightmost digit of n and leftmost digit of n' are coalesced.

%I A258084 #14 Jul 19 2015 09:26:44
%S A258084 2,3,5,7,10,13,15,18,19,31,35,37,38,72,75,78,79,91,92,100,103,105,106,
%T A258084 113,114,124,127,128,133,138,139,143,147,154,155,163,165,166,174,179,
%U A258084 181,184,193,198,199,301,302,304,307,308,315,323,324,335,345,348,351
%N A258084 Numbers n such that n concatenated with its reversal n' yields a prime when the rightmost digit of n and leftmost digit of n' are coalesced.
%C A258084 Alternatively, numbers n such that if n is concatenated with its reversal n', blending together the rightmost digit of n and the leftmost digit of n' yields a prime.
%C A258084 Leading zeros of n’ are discarded. For example, with 100, the reversal is 001; discarding its leading zeros gives 1; since the rightmost digit of 100 does not coincide with the leftmost digit 1 of n’, discard the rightmost digit of 100 - that results in the concatenated number 101, which is prime.
%C A258084 All the terms in this sequence will generate (probably) palindromic primes.
%H A258084 K. D. Bajpai, <a href="/A258084/b258084.txt">Table of n, a(n) for n = 1..5493</a>
%e A258084 a(6) = 13: Reversal of its digits gives 31. Concatenating 13 with 31, blending together 3's, results in 131, which is prime.
%e A258084 a(26) = 124: Reversal of its digits gives 421. Concatenating 124 with 421, blending together 4's, results in 12421, which is prime.
%t A258084 Select[Range[1, 1200], PrimeQ[FromDigits[Join[IntegerDigits [FromDigits [Join[Most [IntegerDigits[#]]]]], IntegerDigits[FromDigits [Reverse[IntegerDigits[#]]]]]] ] &]
%o A258084 (PARI) for(n=1,200,d=digits(n);m=(10^#d)*floor(n/10);s=sum(i=1,#d,d[i]*10^(i-1));if(isprime(m+s),print1(n,", "))) \\ _Derek Orr_, Jun 22 2015
%Y A258084 Cf. A000040, A004086, A054217, A054218.
%K A258084 nonn,base
%O A258084 1,1
%A A258084 _K. D. Bajpai_, May 19 2015