A152242 Integers formed by concatenating primes.

2, 3, 5, 7, 11, 13, 17, 19, 22, 23, 25, 27, 29, 31, 32, 33, 35, 37, 41, 43, 47, 52, 53, 55, 57, 59, 61, 67, 71, 72, 73, 75, 77, 79, 83, 89, 97, 101, 103, 107, 109, 112, 113, 115, 117, 127, 131, 132, 133, 135, 137, 139, 149, 151, 157, 163, 167, 172, 173, 175, 177, 179

Offset

1,1

Comments

Leading zeros are not allowed (cf. A166504).

For any k > 0, there are A246806(k) terms with k digits. - Rémy Sigrist, Jan 08 2023

Links

Rémy Sigrist, Table of n, a(n) for n = 1..10000

Henri Picciotto, Selected Integer Sequences

Example

101 is a member since it is prime; 303 is not since it is composite and 30 is also not a prime.

Prog

(PARI) is_A152242(n)=/* If n is even, the last digit must be 2 and [n\10] (if nonzero) must be in this sequence. (This check is not necessary but improves speed.) */ bittest(n, 0) || return( n%10==2 && (n<10 || is_A152242(n\10))); isprime(n) && return(1); for(i=1, #Str(n)-1, n%10^i>10^(i-1) && isprime( n%10^i ) && is_A152242( n\10^i) && return(1)) \\ M. F. Hasler, Oct 15 2009; edited Oct 16 2009, to disallow leading zeros

Crossrefs

Cf. A019549, A038692, A066737, A105184, A129800, A166504, A246806.

Sequence in context: A106317 A246281 A369331 * A166504 A095405 A206159

Adjacent sequences: A152239 A152240 A152241 * A152243 A152244 A152245

Keyword

nonn,base

Author

Eric Angelini, Oct 15 2009

Extensions

More terms from M. F. Hasler and Zak Seidov, Oct 15 2009

Status

approved