A274214 - OEIS

A274214

Numbers k such that 4*10^k + 63 is prime.

0, 1, 2, 4, 6, 9, 11, 14, 16, 26, 54, 74, 111, 130, 152, 253, 345, 607, 686, 1590, 2711, 5462, 7021, 8681, 11044, 18132, 24072, 25211, 44332, 52792, 85881

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OFFSET

1,3

COMMENTS

For k > 1, numbers k such that the digit 4 followed by k-2 occurrences of the digit 0 followed by the digits 63 is prime (see Example section).

a(32) > 2*10^5.

LINKS

Table of n, a(n) for n=1..31.

Makoto Kamada, Factorization of near-repdigit-related numbers.

Makoto Kamada, Search for 40w63.

EXAMPLE

4 is in this sequence because 4*10^4 + 63 = 40063 is prime.

Initial terms and associated primes:

a(1) = 0, 67;

a(2) = 1, 103;

a(3) = 2, 463;

a(4) = 4, 40063;

a(5) = 6, 4000063, etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[4*10^# + 63] &]

PROG

(PARI) is(n)=ispseudoprime(4*10^n + 63) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.

Sequence in context: A163057 A242137 A138326 * A276223 A288468 A271906

Adjacent sequences: A274211 A274212 A274213 * A274215 A274216 A274217

KEYWORD

nonn,more

AUTHOR

Robert Price, Jun 13 2016

STATUS

approved