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A032721 n prefixed by '4' and followed by '7' is a prime. 1
5, 6, 8, 12, 15, 17, 21, 29, 32, 33, 35, 39, 44, 45, 50, 51, 54, 56, 59, 63, 65, 78, 81, 87, 93, 95, 96, 98, 101, 104, 105, 107, 111, 117, 122, 125, 135, 138, 146, 150, 159, 161, 162, 164, 168, 173, 177, 188, 189, 192, 194, 195, 201, 215, 218, 219, 222, 225 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
LINKS
MATHEMATICA
Select[Range[300], PrimeQ[FromDigits[Join[{4}, IntegerDigits[#], {7}]]]&] (* Harvey P. Dale, Jan 08 2019 *)
CROSSREFS
Sequence in context: A047321 A033158 A193569 * A105106 A140504 A120131
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, May 15 1998
STATUS
approved

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Last modified April 15 20:47 EDT 2024. Contains 371696 sequences. (Running on oeis4.)