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A256048 Smallest palindromic prime by adding at least one digit to both the left and right of n 2

%I

%S 101,313,727,131,11411,151,10601,373,181,191,30103,1114111,1120211,

%T 11311,11411,31513,1160611,1117111,18181,71917,30203,1120211,72227,

%U 32323,12421,1250521,36263,12721,12821,39293,10301,11311,32323,13331,14341,33533,16361,77377

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

%H Chai Wah Wu, <a href="/A256048/b256048.txt">Table of n, a(n) for n = 0..10000</a>

%o (Python)

%o from __future__ import division

%o from sympy import isprime

%o def palgenrange2(m,l): # generator of odd-length palindromes of length at least m and at most 2*l

%o ....if m == 1:

%o ........yield 0

%o ....for x in range(m//2+1,l+1):

%o ........n = 10**(x-1)

%o ........for y in range(n,n*10):

%o ............s = str(y)

%o ............yield int(s+s[-2::-1])

%o def A256048(n):

%o ....sn = str(n)

%o ....for p in palgenrange2(len(sn)+2,len(sn)+20):

%o ........if sn in str(p)[1:-1] and isprime(p):

%o ............break

%o ....else:

%o ........return 'search limit reached'

%o ....return p # _Chai Wah Wu_, Mar 22 2015

%Y Cf. A090287

%K nonn,base

%O 0,1

%A _Felix Fröhlich_, Mar 10 2015

%E a(10), a(12), a(16), a(18) corrected by _Chai Wah Wu_, Mar 22 2015

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Last modified January 18 14:40 EST 2022. Contains 350455 sequences. (Running on oeis4.)