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A062709
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a(n) = 2^n + 3.
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22
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4, 5, 7, 11, 19, 35, 67, 131, 259, 515, 1027, 2051, 4099, 8195, 16387, 32771, 65539, 131075, 262147, 524291, 1048579, 2097155, 4194307, 8388611, 16777219, 33554435, 67108867, 134217731, 268435459, 536870915, 1073741827, 2147483651
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OFFSET
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0,1
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COMMENTS
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Written in binary a(n) is 1000...00011 for n > 1.
For n >= 2, a(n) is the minimal k for which A000120(k(2^n-1)) is not multiple of n. - Vladimir Shevelev, Jun 05 2009
a(n) = A173921(A000051(n+1)). - Reinhard Zumkeller, Mar 04 2010
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LINKS
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Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (3,-2).
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FORMULA
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a(n) = 2a(n-1) - 3 = A052548(n) + 1 = A000051(n) + 2 = A000079(n) + 3 = A000225(n) + 4 = A030101(A004119(n)) for n > 1.
G.f.: (4 - 7*x)/((1 - 2*x)*(1 - x)).
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EXAMPLE
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a(3) = 2^3 + 3 = 8 + 3 = 11.
a(4) = 2^4 + 3 = 16 + 3 = 19.
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MATHEMATICA
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LinearRecurrence[{3, -2}, {4, 5}, 40] (* Vincenzo Librandi, Jan 31 2012 *)
NestList[2 * # - 3 &, 4, 20] (* Zak Seidov, Mar 28 2015 *)
2^Range[0, 29] + 3 (* Alonso del Arte, Mar 28 2015 *)
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PROG
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(Sage) [gaussian_binomial(n, 1, 2)+4 for n in xrange(0, 32)] # Zerinvary Lajos, May 31 2009
(PARI) a(n)=2^n+3 \\ Charles R Greathouse IV, Jan 30 2012
(MAGMA) [2^n+3: n in [0..40]] // Vincenzo Librandi, Jan 31 2012
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CROSSREFS
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Primes in this sequence are A057733.
Sequence in context: A240118 A237133 A253584 * A242212 A129302 A216536
Adjacent sequences: A062706 A062707 A062708 * A062710 A062711 A062712
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KEYWORD
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nonn,easy
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AUTHOR
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Henry Bottomley, Jul 13 2001
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STATUS
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approved
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