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A357076
Numbers k sandwiched between twin primes, such that k times the reverse of k is also sandwiched between twin primes.
0
198, 642, 1050, 2730, 3000, 4050, 4230, 4272, 4548, 4638, 4968, 5010, 6270, 7950, 8970, 9630, 9858, 10092, 11700, 12240, 17490, 18918, 22740, 25470, 33750, 37200, 39240, 45180, 48648, 48732, 48822, 49548, 52182, 53172, 55620, 56532, 57330, 58602, 60918, 65100, 65730, 70140
OFFSET
1,1
COMMENTS
Subsequence of A014574.
EXAMPLE
198 is sandwiched between two twin primes 197 and 199. 176418 = 198*891 is also sandwiched between two twin primes. Thus, 198 is in this sequence.
MATHEMATICA
Select[Range[100000], PrimeQ[# - 1] && PrimeQ[# + 1] && PrimeQ[# FromDigits[Reverse[IntegerDigits[#]]] - 1] && PrimeQ[# FromDigits[Reverse[IntegerDigits[#]]] + 1] &]
PROG
(Python)
from sympy import isprime
def sw(n): return isprime(n-1) and isprime(n+1)
def ok(n): return n%2 == 0 and sw(n) and sw(n*int(str(n)[::-1]))
print([k for k in range(10**5) if ok(k)]) # Michael S. Branicky, Sep 10 2022
CROSSREFS
Cf. A014574.
Sequence in context: A238765 A066218 A304614 * A252952 A252945 A158222
KEYWORD
nonn,base
AUTHOR
Tanya Khovanova, Sep 10 2022
STATUS
approved