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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.)