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 A034814 Concatenations C1 and C2 are both prime (see the comment lines). 0
 9, 51, 63, 87, 111, 123, 153, 177, 207, 211, 239, 263, 273, 289, 327, 333, 343, 359, 407, 471, 489, 497, 513, 541, 597, 621, 651, 659, 663, 681, 687, 693, 697, 747, 753, 793, 819, 831, 869, 909, 977, 987, 1027, 1041, 1089, 1131, 1143, 1239, 1491, 1611 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS C1 = 'prevprime(n) followed by n' C2 = 'n followed by prevprime(n)' LINKS Table of n, a(n) for n=0..49. EXAMPLE n=747 -> previous prime is 743, thus '743747' and '747743' are both primes. CROSSREFS Cf. A034808-A034821. Sequence in context: A221246 A002462 A210061 * A034816 A140381 A330805 Adjacent sequences: A034811 A034812 A034813 * A034815 A034816 A034817 KEYWORD nonn,base AUTHOR Patrick De Geest, Oct 15 1998 STATUS approved

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Last modified September 22 08:19 EDT 2023. Contains 365519 sequences. (Running on oeis4.)