

A271360


Numbers k such that 5*10^k + 87 is prime.


0



1, 2, 3, 4, 6, 16, 38, 39, 46, 61, 62, 100, 116, 152, 190, 298, 472, 642, 688, 1676, 1971, 2338, 4389, 4520, 4986, 7765, 9428, 10820, 18984, 19797, 35360, 42146, 168807
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OFFSET

1,2


COMMENTS

For k>1, numbers such that the digit 5 followed by k2 occurrences of the digit 0 followed by the digits 87 is prime (see Example section).
a(34) > 2*10^5.


LINKS

Table of n, a(n) for n=1..33.
Makoto Kamada, Search for 50w87.


EXAMPLE

3 is in this sequence because 5*10^3 + 87 = 5087 is prime.
Initial terms and primes associated:
a(1) = 1, 137;
a(2) = 2, 587;
a(3) = 3, 5087;
a(4) = 4, 50087;
a(5) = 6, 5000087, etc.


MATHEMATICA

Select[Range[0, 100000], PrimeQ[5*10^# + 87] &]


PROG

(PARI) is(n)=ispseudoprime(5*10^n + 87) \\ Charles R Greathouse IV, Jun 13 2017


CROSSREFS

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.
Sequence in context: A102946 A026094 A285191 * A236413 A069860 A084391
Adjacent sequences: A271357 A271358 A271359 * A271361 A271362 A271363


KEYWORD

nonn,more


AUTHOR

Robert Price, Apr 05 2016


EXTENSIONS

a(33) from Robert Price, Feb 24 2019


STATUS

approved



