A030460 Previous prime concatenated with this prime p is a prime.

3, 37, 89, 157, 163, 173, 211, 239, 257, 263, 269, 277, 337, 359, 379, 439, 479, 521, 541, 547, 607, 659, 673, 683, 733, 947, 977, 1019, 1039, 1187, 1193, 1213, 1229, 1277, 1373, 1459, 1471, 1663, 1693, 1721, 1747, 1867, 1979, 2081, 2179

Offset: 1

Author

Patrick De Geest

Keywords

• nonn
• base

Comments

Terms 157, 257, 263, 541, 1187, 1459, 2179 also belong to A030459. [Carmine Suriano, Jan 27 2011]

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..10000 [extending M.F. Hasler's prior b-File beyond n=4110]

Programs

Mathematica

Transpose[Select[Partition[Prime[Range[400]],2,1], PrimeQ[FromDigits[ Flatten[IntegerDigits/@#]]]&]][[2]] (* Harvey P. Dale, Dec 23 2011 *)

PARI

c=0; o=2; s=1; forprime(p=3,default(primelimit), p>s & s*=10; isprime(o*s+o=p) & write("b030460.txt",c++," ",p))  \\ M. F. Hasler, Feb 06 2011

Formula

A030459(n) = A151799(a(n)). - M. F. Hasler, Feb 06 2011

A030461(n) = concat(A030459(n),a(n)) = A045533( A000720( A030459(n))). - M. F. Hasler, Feb 06 2011

Extensions

Offset changed from 0 to 1 by M. F. Hasler, Feb 06 2011