login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A337834 If k is the n-th number ending in 1,3,7, or 9, a(n) is the least prime > k ending in k. 3
11, 13, 17, 19, 211, 113, 317, 419, 421, 223, 127, 229, 131, 233, 137, 139, 241, 443, 347, 149, 151, 353, 157, 359, 461, 163, 167, 269, 271, 173, 277, 179, 181, 283, 487, 389, 191, 193, 197, 199, 5101, 1103, 5107, 1109, 2111, 2113, 1117, 3119, 3121, 1123, 4127, 1129, 2131, 4133, 2137, 4139, 2141 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n) exists by Dirichlet's theorem on primes in arithmetic progressions.

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

Index entries for primes involving decimal expansion of n

EXAMPLE

For n=3 the third number ending in 1,3,7 or 9 is 7 and the least prime > 7 ending in 7 is a(3)=17.

For n=12 the 12th number ending in 1,3,7 or 9 is 29 and the least prime > 29 ending in 29 is a(12)=229.

MAPLE

f:= proc(n) local d, x;

  d:= ilog10(n)+1;

  for x from n + 10^d by 10^d do

    if isprime(x) then return x fi

  od

end proc:

map(f, [seq(seq(10*i+j, j=[1, 3, 7, 9]), i=0..99)];

CROSSREFS

Sequence in context: A327349 A240899 A090149 * A089691 A036979 A036977

Adjacent sequences:  A337831 A337832 A337833 * A337835 A337836 A337837

KEYWORD

nonn,base

AUTHOR

Robert Israel, Sep 24 2020

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 June 13 17:14 EDT 2021. Contains 345008 sequences. (Running on oeis4.)