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!)
A271438 Numbers n such that the number formed by concatenating in ascending order the first n multidigit palindromic primes is prime. 0
1, 17, 451 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..3.

G. L. Honaker, Jr. and C. Caldwell, 11101...10301 (52-digits), Prime Curios!.

EXAMPLE

Concatenating in ascending order the 17 smallest palindromic primes with at least two digits gives 1110113115118119131335337338372775778779791992910301, which is prime, so 17 is a term of the sequence.

PROG

(PARI) nextpalprime(n) = my(p=nextprime(n)); while(p!=eval(concat(Vecrev(Str(p)))), p=nextprime(p+1)); p

terms(n) = my(i=0, k=1, s="", p=10); while(i < n, p=nextpalprime(p+1); s=Str(s, p); if(ispseudoprime(eval(s)), print1(k, ", "); i++); k++)

terms(3) \\ print initial three terms

CROSSREFS

Cf. A002385.

Sequence in context: A301642 A035022 A012117 * A122430 A009051 A035276

Adjacent sequences:  A271435 A271436 A271437 * A271439 A271440 A271441

KEYWORD

nonn,base,more,bref

AUTHOR

Felix Fröhlich, Apr 07 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 July 15 23:32 EDT 2020. Contains 335774 sequences. (Running on oeis4.)