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

 

Logo

Annual Appeal: Please make a donation to keep the OEIS running. In 2018 we replaced the server with a faster one, added 20000 new sequences, and reached 7000 citations (often saying "discovered thanks to the OEIS").
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A064507 Numbers of more than one digit that yield primes when cast in their own base. 2
21, 27, 29, 61, 67, 111, 151, 191, 201, 203, 223, 241, 313, 319, 331, 351, 373, 397, 403, 409, 461, 463, 481, 553, 559, 571, 667, 711, 791, 807, 841, 869, 889, 931, 979, 1071, 1079, 1107, 1129, 1189, 1257, 1273, 1277, 1297, 1431, 1437, 1583, 1611, 1639 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All terms are coprime to 10. - Robert Israel, Dec 04 2016

LINKS

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

EXAMPLE

E.g. 21 in base 21 is 2*21+1=43, 111 is 1*111*111+1*111+1=12433, etc.

MAPLE

filter:= proc(n) local L, i;

   L:= convert(n, base, 10);

   isprime(add(L[i]*n^(i-1), i=1..nops(L)))

end proc:

select(filter, [seq(i, i=11..2000, 2)]); # Robert Israel, Dec 04 2016

PROG

(PARI) isok(n) = (n>=10) && isprime(fromdigits(digits(n), n)); \\ Michel Marcus, Dec 04 2016

CROSSREFS

Cf. A064508.  Contained in A054684.

Sequence in context: A299594 A318544 A173836 * A249729 A280107 A264102

Adjacent sequences:  A064504 A064505 A064506 * A064508 A064509 A064510

KEYWORD

nonn,base

AUTHOR

Jon Perry, Oct 06 2001

EXTENSIONS

Offset corrected by Arkadiusz Wesolowski, Oct 19 2013

Name corrected by Robert Israel, Dec 04 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 December 18 16:33 EST 2018. Contains 318229 sequences. (Running on oeis4.)