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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A101782 Upper bound of twin prime pairs whose digital reverse is prime. 0
5, 7, 13, 31, 73, 151, 181, 199, 313, 1021, 1033, 1153, 1231, 1279, 1321, 1429, 1453, 1669, 1723, 1789, 1879, 1933, 3121, 3169, 3301, 3373, 3391, 3463, 3469, 3541, 3583, 3853, 7459, 7561, 7879, 7951, 9001, 9013, 9241, 9421, 9439, 9679, 9721, 9769, 9931 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..45.

EXAMPLE

13 is the upper bound of twin prime pair (11,13) and its digital reverse, 31, is prime.

PROG

(PARI) twurpr(n) = { for(x=1, n, y=twinu(x); z=eval(rev(y)); if(isprime(z), print1(y", ")) ) } twinu(n) = \The n-th upper twin prime { local(c, x); c=0; x=1; while(c<n, if(isprime(prime(x)+2), c++); x++; ); return(prime(x)) } rev(str) = \ Get the reverse of the input string { local(tmp, s, j); tmp = Vec(Str(str)); s=""; forstep(j=length(tmp), 1, -1, s=concat(s, tmp[j])); return(s) }

CROSSREFS

Sequence in context: A241859 A179625 A141191 * A168609 A266951 A102903

Adjacent sequences:  A101779 A101780 A101781 * A101783 A101784 A101785

KEYWORD

easy,nonn,base

AUTHOR

Cino Hilliard, Jan 26 2005

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified April 30 16:28 EDT 2017. Contains 285670 sequences.