A357076 Numbers k sandwiched between twin primes, such that k times the reverse of k is also sandwiched between twin primes.

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.

Links

Table of n, a(n) for n=1..42.

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

Adjacent sequences: A357073 A357074 A357075 * A357077 A357078 A357079

Keyword

nonn,base

Author

Tanya Khovanova, Sep 10 2022

Status

approved