A263242 -id:A263242 - cp's OEIS frontend

A263240 Emirps whose reversals are merely their end digits swapped.

13, 17, 31, 37, 71, 73, 79, 97, 107, 113, 149, 157, 167, 179, 199, 311, 337, 347, 359, 389, 701, 709, 733, 739, 743, 751, 761, 769, 907, 937, 941, 953, 967, 971, 983, 991, 1009, 1223, 1229, 1559, 1669, 3221, 3889, 7229, 9001, 9221, 9227, 9551, 9661, 10007, 10009, 10909, 11717, 11719, 12227, 12323, 12829, 13337, 13933, 14143, 14447, 14449, 14549, 14843, 14947

Offset: 1

Lekraj Beedassy, Oct 13 2015

Subsequence of emirps A006567 with which it is identical for the first 37 terms.

Entries with 4 or more digits consist of a middle repdigit or palindrome part inserted between the end digits.

Cf. A006567, A263241, A263242.

A263241 Lesser of emirp pairs that are merely reversals of their end digits.

Original entry on oeis.org

13, 17, 37, 79, 107, 113, 149, 157, 167, 179, 199, 337, 347, 359, 389, 709, 739, 769, 1009, 1223, 1229, 1559, 1669, 3889, 7229, 10007, 10009, 10909, 11717, 11719, 12227, 12323, 12829, 13337, 13933, 14143, 14447, 14449, 14549, 14843, 14947, 15053, 16063, 16267, 16567, 16763

Offset: 1

Lekraj Beedassy, Oct 13 2015

The first digit is always smaller than last digit.

Cf. A006567, A109308, A263240, A263242.

Select[Range[20000], And @@ PrimeQ[{#, IntegerReverse[#]}] && ! PalindromeQ[#] && First[(d = IntegerDigits[#])] < Last[d] && PalindromeQ[Most@ Rest@ IntegerDigits[#]] &] (* Amiram Eldar, Oct 16 2021 *)

isok(p) = my(dp=digits(p), dr=Vecrev(dp), r=fromdigits(dr)); if (isprime(r) && (r>p) && isprime(p), sum(i=2, #dp-1, dp[i]==dr[i]) == #dp-2); \\ Michel Marcus, Oct 16 2021

Missing 179 added by Zak Seidov, Oct 15 2021

cp's OEIS Frontend

A263240 Emirps whose reversals are merely their end digits swapped.

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A263241 Lesser of emirp pairs that are merely reversals of their end digits.

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