A256048 Smallest palindromic prime by adding at least one digit to both the left and right of n

101, 313, 727, 131, 11411, 151, 10601, 373, 181, 191, 30103, 1114111, 1120211, 11311, 11411, 31513, 1160611, 1117111, 18181, 71917, 30203, 1120211, 72227, 32323, 12421, 1250521, 36263, 12721, 12821, 39293, 10301, 11311, 32323, 13331, 14341, 33533, 16361, 77377

Offset

0,1

Links

Chai Wah Wu, Table of n, a(n) for n = 0..10000

Prog

(Python)
from __future__ import division
from sympy import isprime
def palgenrange2(m, l): # generator of odd-length palindromes of length at least m and at most 2*l
....if m == 1:
........yield 0
....for x in range(m//2+1, l+1):
........n = 10**(x-1)
........for y in range(n, n*10):
............s = str(y)
............yield int(s+s[-2::-1])
def A256048(n):
....sn = str(n)
....for p in palgenrange2(len(sn)+2, len(sn)+20):
........if sn in str(p)[1:-1] and isprime(p):
............break
....else:
........return 'search limit reached'
....return p # Chai Wah Wu, Mar 22 2015

Crossrefs

Cf. A090287

Sequence in context: A139701 A195294 A142578 * A252942 A090287 A134971

Adjacent sequences: A256045 A256046 A256047 * A256049 A256050 A256051

Keyword

nonn,base

Author

Felix Fröhlich, Mar 10 2015

Extensions

a(10), a(12), a(16), a(18) corrected by Chai Wah Wu, Mar 22 2015

Status

approved