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 A089757 Distinct multiples of 3 such that the concatenation of a(n), a(n-1), ..., a(2), a(1), 1 is a prime and a(n) > a(n-1). 1
 3, 6, 9, 12, 27, 30, 39, 42, 66, 162, 231, 252, 258, 273, 276, 411, 474, 531, 543, 642, 699, 732, 795, 819, 1023, 1059, 1101, 1257, 1281, 1842, 1872, 1902, 1953, 2028, 2076, 2223, 2331, 2922, 3063, 3102, 3414, 3522, 3624, 3714, 3867, 4320, 4383, 4482, 4788 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 LINKS EXAMPLE 31, 631, 9631, 129631, etc. are primes. a(10) = 231 because 2311626642393027129631 is prime. MAPLE ds:=proc(s) local j: RETURN(add(s[j]*10^(j-1), j=1..nops(s))): end: a:=[]: k1:=1: for n from 1 to 50 do for k from k1 do m:=ds([1, seq(op(convert(a[i], base, 10)), i=1..nops(a)), op(convert(3*k, base, 10))]): if isprime(m) then k1:=k+1: a:=[op(a), 3*k]: break fi od od: op(a); # C. Ronaldo CROSSREFS Cf. A089758. Sequence in context: A233155 A118519 A282762 * A294569 A277250 A083491 Adjacent sequences:  A089754 A089755 A089756 * A089758 A089759 A089760 KEYWORD base,nonn AUTHOR Amarnath Murthy, Nov 22 2003 EXTENSIONS More terms from Jim Nastos, Jan 31 2004 More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Dec 26 2004 STATUS approved

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Last modified July 29 04:38 EDT 2021. Contains 346340 sequences. (Running on oeis4.)