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 A249407 Numbers not in A249406. 4
 2, 3, 4, 5, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Primes are a subsequence, but semiprimes (cf. A001358) are not: first missing: A249406(1)=6=2*3, A249406(732)=2196323=1481*1483, A249406(1263)=6502499=2549*2551, A249406(1472)=8820899=2969*2971, A249406(1756)=12531599=3539*3541, ... ; see A249411 for numbers of the form m*(m+1). LINKS Table of n, a(n) for n=1..66. PROG (Haskell) import Data.List ((\\)) a249407 n = a249407_list !! (n-1) a249407_list = f [2..] where f ws@(u:v:_) = u : v : f (ws \\ [u, v, u * v]) CROSSREFS Cf. A249406 (complement), A000040 (subsequence), A001358. Sequence in context: A080907 A127161 A129657 * A360305 A103679 A029916 Adjacent sequences: A249404 A249405 A249406 * A249408 A249409 A249410 KEYWORD nonn AUTHOR Reinhard Zumkeller, Oct 31 2014 STATUS approved

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Last modified December 1 13:31 EST 2023. Contains 367475 sequences. (Running on oeis4.)