

A271646


Numbers n such that 22*10^n+7 is prime.


0



0, 1, 2, 9, 13, 14, 15, 17, 22, 23, 80, 297, 393, 524, 591, 1107, 1135, 1179, 1442, 2819, 3549, 3756, 3837, 4903, 5277, 5639, 7230, 13147, 14828, 16158, 18119, 28880, 99275
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OFFSET

1,3


COMMENTS

For n>1, numbers such that the digits 22 followed by n1 occurrences of the digit 0 followed by the digit 7 is prime (see Example section).
a(34) > 10^5.


LINKS

Table of n, a(n) for n=1..33.
Makoto Kamada, Factorization of nearrepdigitrelated numbers.
Makoto Kamada, Search for 220w7.


EXAMPLE

2 is in this sequence because 22*10^2+7 = 227 is prime.
Initial terms and primes associated:
a(1) = 0, 29;
a(2) = 1, 227;
a(3) = 2, 2207;
a(4) = 9, 22000000007;
a(5) = 13, 220000000000007, etc.


MATHEMATICA

Select[Range[0, 100000], PrimeQ[22*10^#+7] &]


PROG

(PARI) is(n)=ispseudoprime(22*10^n+7) \\ Charles R Greathouse IV, Jun 13 2017


CROSSREFS

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.
Sequence in context: A225548 A233400 A234945 * A024976 A171234 A287069
Adjacent sequences: A271643 A271644 A271645 * A271647 A271648 A271649


KEYWORD

nonn,more


AUTHOR

Robert Price, Apr 11 2016


STATUS

approved



