A245877 Primes p such that p - d and p + d are also primes, where d is the largest digit of p.
263, 563, 613, 653, 1613, 1663, 3463, 4643, 5563, 5653, 6263, 6323, 12653, 13463, 14633, 16063, 16223, 21163, 21563, 25463, 26113, 30643, 32063, 33623, 36313, 41263, 41603, 44263, 53623, 54623, 56003, 60133, 61553, 62213, 62633, 64013, 65413, 105613, 106213
Offset: 1
Examples
The prime 263 is in the sequence because 263 - 6 = 257 and 263 + 6 = 269 are both primes.
Links
- Harvey P. Dale, Table of n, a(n) for n = 1..1000
Programs
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Mathematica
pdpQ[n_]:=Module[{m=Max[IntegerDigits[n]]},AllTrue[n+{m,-m},PrimeQ]]; Select[ Prime[Range[11000]],pdpQ] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Jan 13 2017 *) -
PARI
select(p->d=vecsort(digits(p),,4)[1]; isprime(p-d) && isprime(p+d), primes(20000))
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Python
import sympy from sympy import prime from sympy import isprime for n in range(1,10**5): s=prime(n) lst = [] for i in str(s): lst.append(int(i)) if isprime(s+max(lst)) and isprime(s-max(lst)): print(s,end=', ') # Derek Orr, Aug 13 2014
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