

A275524


Numbers n such that (56*10^n + 223)/9 is prime.


0



0, 2, 3, 5, 8, 32, 36, 53, 92, 126, 156, 158, 536, 639, 846, 1356, 1953, 2237, 4407, 5082, 17447, 17922, 24806, 25926, 29699, 30474, 37424, 63942
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OFFSET

1,2


COMMENTS

For n>1, numbers such that the digit 6 followed by n2 occurrences of the digit 2 followed by the digits 47 is prime (see Example section).
a(29) > 10^5.


LINKS

Table of n, a(n) for n=1..28.
Makoto Kamada, Factorization of nearrepdigitrelated numbers.
Makoto Kamada, Search for 62w47.


EXAMPLE

3 is in this sequence because (56*10^3 + 223)/9 = 6247 is prime.
Initial terms and primes associated:
a(1) = 0, 31;
a(2) = 2, 647;
a(3) = 3, 6247;
a(4) = 5, 622247;
a(5) = 8, 622222247, etc.


MATHEMATICA

Select[Range[0, 100000], PrimeQ[(56*10^# + 223)/9] &]


PROG

(MAGMA) [n: n in [0..500]  IsPrime((56*10^n+223) div 9)]; // Vincenzo Librandi, Aug 01 2016
(PARI) is(n)=ispseudoprime((56*10^n+223)/9) \\ Charles R Greathouse IV, Jun 13 2017


CROSSREFS

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.
Sequence in context: A273003 A014258 A237575 * A177195 A178355 A281618
Adjacent sequences: A275521 A275522 A275523 * A275525 A275526 A275527


KEYWORD

nonn,more


AUTHOR

Robert Price, Jul 31 2016


STATUS

approved



