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 A083792 Lexicographically first increasing sequence such that no two successive terms have the same prime signature. 2
 1, 2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 18, 19, 20, 21, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 36, 37, 38, 40, 41, 42, 43, 44, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 77, 78, 79, 80, 81 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Alois P. Heinz, Table of n, a(n) for n = 1..20000 EXAMPLE From Jon E. Schoenfield, Aug 13 2017: (Start) a(1) = 1 (which has no prime factors); a(2) = 2 (a prime); a(3) cannot be 3, because 2 and 3 have the same prime signature (each is a prime); however, the prime signature of 4 (the square of a prime) differs from that of 2, so a(3) = 4. (End) MAPLE s:= n-> sort(map(i-> i[2], ifactors(n)[2])): a:= proc(n) option remember; local k; for k from       1+a(n-1) while s(k)=s(a(n-1)) do od; k     end: a(1):=1: seq(a(n), n=1..80);  # Alois P. Heinz, Mar 09 2018 MATHEMATICA {1, 2} ~Join~ Select[Range[2, 80], Last /@ FactorInteger[#] != Last /@ FactorInteger[# - 1] &] (* Giovanni Resta, Aug 14 2017 *) CROSSREFS Cf. A083793. Sequence in context: A094798 A326178 A162880 * A083794 A133016 A026503 Adjacent sequences:  A083789 A083790 A083791 * A083793 A083794 A083795 KEYWORD easy,nonn AUTHOR Amarnath Murthy, May 07 2003 EXTENSIONS More terms from James A. Sellers, May 19 2003 Incorrect term 76 removed by Alois P. Heinz, Mar 09 2018 STATUS approved

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Last modified July 21 06:55 EDT 2019. Contains 325192 sequences. (Running on oeis4.)