A062351 Palindromic primes with strictly increasing digits up to the middle and then strictly decreasing.

2, 3, 5, 7, 11, 131, 151, 181, 191, 353, 373, 383, 787, 797, 12421, 12721, 12821, 13831, 13931, 14741, 17971, 34543, 34843, 35753, 1235321, 1245421, 1257521, 1268621, 1278721, 1456541, 1469641, 1489841, 1579751, 1589851, 3479743

Offset

1,1

Comments

The last term of the finite series is a(63) = 123467898764321.

Links

Nathaniel Johnston, Table of n, a(n) for n = 1..63 (complete sequence)

Patrick De Geest, World of Palindromic Primes

Example

13831 belongs to the sequence as it is a palindromic prime in which the digits are increasing up to the middle digit 8 and then decreasing.

Prog

(Python)
from sympy import isprime
from itertools import combinations
def agen():
  for digits in range(1, 19):
    for left in combinations("123456789", (digits+1)//2):
      left = "".join(left)
      yield int(left + (left[:digits//2])[::-1])
print(list(filter(isprime, agen()))) # Michael S. Branicky, Apr 25 2021

Crossrefs

Cf. A343524 (strictly increasing palindromes), A062352, A084836.

Sequence in context: A049575 A070028 A084836 * A185267 A088249 A241724

Adjacent sequences: A062348 A062349 A062350 * A062352 A062353 A062354

Keyword

nonn,base,easy,fini,full

Author

Amarnath Murthy, Jun 23 2001

Extensions

Corrected and edited by Patrick De Geest, Jun 07 2003

Status

approved