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 A081547 Smallest composite number which is 1 more than the product of n (not necessarily distinct) prime numbers. 2
 4, 10, 9, 25, 33, 65, 129, 385, 513, 1025, 2049, 4097, 8193, 16385, 32769, 98305, 131073, 262145, 524289, 1048577, 2097153, 4194305, 8388609, 16777217, 33554433, 67108865, 134217729, 268435457, 536870913, 1073741825, 2147483649 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(2*n+1) = 2^(2*n+1)+1, n>0. - Vladeta Jovovic, Apr 02 2003 LINKS Harvey P. Dale, Table of n, a(n) for n = 1..1000 FORMULA For n>2, a(n) = 2^n+1 unless this is a Fermat prime (A019434), in which case a(n) = 2^(n-1)*3+1 (which is divisible by 5). - Dean Hickerson, Apr 05 2003 MATHEMATICA cno[n_]:=Module[{a=2^n+1}, If[PrimeQ[a], 2^(n-1)*3+1, a]]; Join[{4, 10}, Array[cno, 30, 3]] (* Harvey P. Dale, Mar 24 2012 *) CROSSREFS Cf. A081545, A081546, A081548, A073919, A007583. Sequence in context: A320577 A199805 A053248 * A264272 A264257 A111072 Adjacent sequences: A081544 A081545 A081546 * A081548 A081549 A081550 KEYWORD nonn AUTHOR Amarnath Murthy, Apr 01 2003 EXTENSIONS More terms from Vladeta Jovovic, Apr 02 2003 STATUS approved

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Last modified May 22 10:22 EDT 2024. Contains 372745 sequences. (Running on oeis4.)