OFFSET
1,1
COMMENTS
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.
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.
All the terms in this sequence will generate (probably) palindromic primes.
LINKS
K. D. Bajpai, Table of n, a(n) for n = 1..5493
EXAMPLE
a(6) = 13: Reversal of its digits gives 31. Concatenating 13 with 31, blending together 3's, results in 131, which is prime.
a(26) = 124: Reversal of its digits gives 421. Concatenating 124 with 421, blending together 4's, results in 12421, which is prime.
MATHEMATICA
Select[Range[1, 1200], PrimeQ[FromDigits[Join[IntegerDigits [FromDigits [Join[Most [IntegerDigits[#]]]]], IntegerDigits[FromDigits [Reverse[IntegerDigits[#]]]]]] ] &]
PROG
(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
CROSSREFS
KEYWORD
nonn,base
AUTHOR
K. D. Bajpai, May 19 2015
STATUS
approved