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 A032720 Integers that when prefixed by '3' and followed by '7' yield a prime. 0
 0, 1, 3, 4, 6, 9, 13, 16, 18, 21, 25, 30, 34, 40, 45, 46, 51, 52, 54, 55, 60, 61, 63, 67, 69, 72, 76, 79, 84, 87, 90, 91, 94, 96, 114, 117, 123, 124, 126, 127, 130, 132, 133, 135, 138, 139, 147, 151, 154, 156, 160, 162, 165, 166, 168, 172, 181, 184, 190, 195 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Table of n, a(n) for n=1..60. MAPLE q:= k-> isprime(parse(""||3||k||7)): select(q, [\$0..200])[]; # Alois P. Heinz, Jul 16 2022 MATHEMATICA Select[Range[0, 250], PrimeQ[FromDigits[Join[{3}, IntegerDigits[#], {7}]]]&] (* Harvey P. Dale, Dec 19 2010 *) PROG (PARI) isok(k) = isprime(eval(concat(3, concat(Str(k), 7)))); \\ Michel Marcus, Jul 16 2022 CROSSREFS Sequence in context: A140570 A285303 A135072 * A289117 A355697 A167928 Adjacent sequences: A032717 A032718 A032719 * A032721 A032722 A032723 KEYWORD nonn,base AUTHOR Patrick De Geest, May 15 1998 EXTENSIONS Name edited and offset 1 from Michel Marcus, Jul 16 2022 STATUS approved

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Last modified May 28 12:54 EDT 2024. Contains 372913 sequences. (Running on oeis4.)