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A152242 Integers formed by concatenating primes. 12
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Leading zeros are not allowed (cf. A166504).

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

CROSSREFS

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

Sequence in context: A318719 A106317 A246281 * A166504 A095405 A242127

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

PARI code modified to disallow leading zeros. - M. F. Hasler, Oct 16 2009

STATUS

approved

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Last modified September 20 00:20 EDT 2021. Contains 347577 sequences. (Running on oeis4.)