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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A232727 Numbers n such that the concatenation n123456789 is prime. 1
28, 32, 41, 55, 56, 59, 74, 95, 100, 116, 119, 122, 124, 142, 154, 161, 164, 179, 184, 193, 200, 215, 217, 220, 230, 241, 259, 265, 278, 296, 298, 314, 332, 382, 392, 406, 409, 416, 424, 425, 439, 452, 455, 458, 460, 466, 475, 493, 496, 514, 515, 530, 536, 559, 572, 574, 598, 602, 613, 629, 634 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers n in the primes of the form n987654321 are listed in A232766. Primes in sequence are in A232728.

LINKS

Table of n, a(n) for n=1..61.

EXAMPLE

278 is a member of this sequence because 278123456789 is prime.

MATHEMATICA

Select[Range[700], PrimeQ[FromDigits[Flatten[{IntegerDigits[#], IntegerDigits[123456789]}]]] &] (* Vincenzo Librandi, Apr 28 2015 *)

PROG

(Python)

from sympy import isprime

{print(n, end=', ') for n in range(1, 10**3) if isprime(int(str(n)+'123456789'))}

## Simplified by Derek Orr, Apr 28 2015

(PARI) for(n=1, 10^3, if(isprime(eval(concat(Str(n), "123456789"))), print1(n, ", "))) \\ Derek Orr, Apr 28 2015

(MAGMA) [n: n in [0..700] | IsPrime(Seqint([9..1 by -1] cat Intseq(n)))]; // Vincenzo Librandi, Apr 28 2015

(Sage) [n for n in (1..700) if is_prime(n*10^9+123456789)] # Bruno Berselli, Apr 28 2015

CROSSREFS

Cf. A104914, A104915, A232728, A232766.

Sequence in context: A057483 A025367 A121018 * A232766 A230855 A090637

Adjacent sequences:  A232724 A232725 A232726 * A232728 A232729 A232730

KEYWORD

nonn,base,easy

AUTHOR

Derek Orr, Nov 29 2013

EXTENSIONS

More terms from Derek Orr, Apr 28 2015

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 April 26 08:04 EDT 2019. Contains 322472 sequences. (Running on oeis4.)