A074857 - OEIS

A074857

Primes p such that all p-pal for p/2 < pal < p are nonprime, where pal is a palindrome.

2, 3, 17, 19, 23, 31, 37, 43, 53, 59, 137, 139, 151, 157, 179, 181, 191, 197, 199, 211, 307, 317, 337, 347, 367, 397, 599, 1423, 1433, 1453, 1483, 1493, 1523, 1543, 1583, 1613, 1693, 1723, 1733, 1753, 1759, 1777, 1783, 1787, 1789, 1801, 1811, 1823, 1831, 1847

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..50.

EXAMPLE

59 is in the sequence because the palindromes between 29 and 59 are 33,44,55 and 59-55 = 4, 59-44 = 15, 59-33 = 26, all composite.

From Sean A. Irvine, Jan 31 2025: (Start)

2 is in the sequence because there are no palindromes between 1 and 2.

3 is in the sequence because the only palindrome between 3/2 and 3 is 2 and 3-2=1 is not prime.

23 is in the sequence because the only palindrome between 23/2 and 23 is 22 and 23-22=1 is not prime. (End)

CROSSREFS

Sequence in context: A090913 A176236 A171139 * A291281 A135931 A215323

Adjacent sequences: A074854 A074855 A074856 * A074858 A074859 A074860

KEYWORD

base,nonn

AUTHOR

Jason Earls, Sep 11 2002

EXTENSIONS

Missing 3 inserted by Sean A. Irvine, Jan 31 2025

STATUS

approved