

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
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OFFSET

1,1


COMMENTS



LINKS



FORMULA

For n>2, a(n) = 2^n+1 unless this is a Fermat prime (A019434), in which case a(n) = 2^(n1)*3+1 (which is divisible by 5).  Dean Hickerson, Apr 05 2003


MATHEMATICA

cno[n_]:=Module[{a=2^n+1}, If[PrimeQ[a], 2^(n1)*3+1, a]]; Join[{4, 10}, Array[cno, 30, 3]] (* Harvey P. Dale, Mar 24 2012 *)


CROSSREFS



KEYWORD

nonn


AUTHOR



EXTENSIONS



STATUS

approved



