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A034814
Concatenations C1 and C2 are both prime (see the comment lines).
2
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
OFFSET
1,1
COMMENTS
C1 = 'prevprime(k) followed by k'.
C2 = 'k followed by prevprime(k)'.
LINKS
EXAMPLE
n=747 -> previous prime is 743, thus '743747' and '747743' are both primes.
CROSSREFS
Intersection of A034808 and A034809.
Sequence in context: A221246 A002462 A210061 * A034816 A140381 A330805
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, Oct 15 1998
EXTENSIONS
Offset changed by Andrew Howroyd, Aug 13 2024
STATUS
approved