login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A271882 Numbers n such that (10^n + 101)/3 is prime. 0
1, 2, 3, 6, 9, 12, 23, 39, 59, 168, 198, 203, 231, 449, 863, 920, 1064, 1484, 1674, 2018, 2943, 3123, 4073, 4122, 8360, 11774, 16031, 26507, 31146, 33170, 44952, 62402, 88020, 89687 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For n>1, numbers that begin with n-2 occurrences of the digit 3 followed by the digits 67 is prime (see Example section).

a(35) > 2*10^5.

LINKS

Table of n, a(n) for n=1..34.

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

Makoto Kamada, Search for 3w67.

EXAMPLE

3 is in this sequence because (10^3+101)/3 = 367 is prime.

Initial terms and primes associated:

a(1) = 1, 37;

a(2) = 2, 67;

a(3) = 3, 367;

a(4) = 6, 333367;

a(5) = 9, 333333367, etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[(10^#+101)/3] &]

PROG

(PARI) lista(nn) = for(n=1, nn, if(ispseudoprime((10^n+101)/3), print1(n, ", "))); \\ Altug Alkan, Apr 16 2016

CROSSREFS

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

Sequence in context: A298435 A261539 A325552 * A123316 A303365 A096845

Adjacent sequences:  A271879 A271880 A271881 * A271883 A271884 A271885

KEYWORD

nonn,more

AUTHOR

Robert Price, Apr 16 2016

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 11 18:50 EST 2019. Contains 329031 sequences. (Running on oeis4.)