The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A083439 a(1) = 3; then a(n+1) = smallest prime not already in the sequence such that the concatenations a(n)a(n+1) and a(n+1)a(n) are both primes. 0
 3, 7, 19, 13, 61, 151, 31, 139, 67, 37, 79, 193, 163, 127, 157, 97, 43, 103, 307, 367, 457, 643, 73, 277, 223, 229, 373, 199, 109, 313, 211, 271, 241, 421, 181, 283, 397, 337, 349, 331, 577, 523, 463, 613, 439, 541, 571, 433, 787, 547, 661, 769, 487, 601, 823, 709 (list; graph; refs; listen; history; text; internal format)
 OFFSET 3,1 LINKS Table of n, a(n) for n=3..58. PROG (PARI) { p=3; S=Set(); while(!setsearch(S, p), S=setunion(S, Set([p])); print1(p, ", "); forprime(q=2, 10^4, if(setsearch(S, q), next); if( isprime(eval(concat(Str(p), Str(q)))) && isprime(eval(concat(Str(q), Str(p)))), p=q; break))) } \\ Max Alekseyev, Apr 24 2009 CROSSREFS Cf. A073641, A075609. Sequence in context: A217371 A088629 A075609 * A151858 A365139 A242170 Adjacent sequences: A083436 A083437 A083438 * A083440 A083441 A083442 KEYWORD base,nonn AUTHOR Amarnath Murthy and Meenakshi Srikanth (menakan_s(AT)yahoo.com), Apr 30 2003 EXTENSIONS Corrected and extended by Max Alekseyev, Apr 24 2009 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified May 24 12:49 EDT 2024. Contains 372773 sequences. (Running on oeis4.)