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 A105184 Primes that can be written as concatenation of two primes in decimal representation. 24
 23, 37, 53, 73, 113, 137, 173, 193, 197, 211, 223, 229, 233, 241, 271, 283, 293, 311, 313, 317, 331, 337, 347, 353, 359, 367, 373, 379, 383, 389, 397, 433, 523, 541, 547, 571, 593, 613, 617, 673, 677, 719, 733, 743, 761, 773, 797, 977, 1013, 1033, 1093 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Primes that can be written as the concatenation of two distinct primes is the same sequence. Number of terms < 10^n: 0, 4, 48, 340, 2563, 19019, 147249, ... - T. D. Noe, Oct 04 2010 LINKS T. D. Noe, Table of n, a(n) for n=1..10000 EXAMPLE 193 is in the sequence because it is the concatenation of the primes 19 and 3. 197 is in the sequence because it is the concatenation of the primes 19 and 7. 199 is not in the sequence because there is no way to break it into two substrings such that both are prime: neither 1 nor 99 is prime, and 19 is prime but 9 is not. MATHEMATICA searchMax = 10^4; Union[Reap[Do[p = Prime[i]; q = Prime[j]; n = FromDigits[Join[IntegerDigits[p], IntegerDigits[q]]]; If[PrimeQ[n], Sow[n]], {i, PrimePi[searchMax/10]}, {j, 2, PrimePi[searchMax/10^Ceiling[Log[10, Prime[i]]]]}]][[2, 1]]] (* T. D. Noe, Oct 04 2010 *) CROSSREFS Subsequence of A019549. Cf. A121608, A121609, A121610, A019549, A083427. Sequence in context: A019549 A272157 A129800 * A238056 A066064 A163759 Adjacent sequences: A105181 A105182 A105183 * A105185 A105186 A105187 KEYWORD nonn,base AUTHOR Lekraj Beedassy, Apr 11 2005 EXTENSIONS Corrected and extended by Ray Chandler, Apr 16 2005 Edited by N. J. A. Sloane, May 03 2007 Edited by N. J. A. Sloane, to remove erroneous b-file, comments and Mma program, Oct 04 2010 STATUS approved

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Last modified February 26 11:46 EST 2024. Contains 370352 sequences. (Running on oeis4.)