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A019460
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Add 1, multiply by 1, add 2, multiply by 2, etc.
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6
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2, 3, 3, 5, 10, 13, 39, 43, 172, 177, 885, 891, 5346, 5353, 37471, 37479, 299832, 299841, 2698569, 2698579, 26985790, 26985801, 296843811, 296843823, 3562125876, 3562125889, 46307636557, 46307636571, 648306911994
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OFFSET
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0,1
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COMMENTS
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After a(7)=43, the next prime in the sequence is a(649) with 676 digits.- M. F. Hasler, Jan 12 2011
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REFERENCES
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New York Times, Oct 13, 1996.
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LINKS
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Table of n, a(n) for n=0..28.
Nick Hobson, Python program for this sequence
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FORMULA
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a(2n) = 2(A000522(n) + n!) - n - 2
a(2n+1) = 2(A000522(n) + n!) - 1
Recursive: a(0) = 2, a(n) = ( 1 + floor((n-1)/2) - ceil((n-1)/2) ) * ( a(n-1) + (n+2)/2 ) + ( ceil((n-1)/2) - floor((n-1)/2) ) * ( (n/2)*a(n-1) ). - Wesley Ivan Hurt, Jan 12 2013
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MATHEMATICA
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a[n_] := If[ OddQ@n, a[n - 1] + (n + 1)/2, a[n - 1]*n/2]; a[0] = 2; Table[ a@n, {n, 0, 28}] (* Robert G. Wilson v, Jul 21 2009 *)
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PROG
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A019460(n)=2*(A000522(n\2)+(n\2)!)-if(bittest(n, 0), 1, n\2+2)
/* For producing the terms in increasing order, the following 'hack' can be used M. F. Hasler, Jan 12 2011 */
lastn=0; an1=1; A000522(n)={ an1=if(n, n==lastn & return(an1); n==lastn+1|error(); an1*lastn=n)+1 }
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CROSSREFS
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Cf. A019463, A019462, A019461, A082448.
Sequence in context: A065460 A175147 A001180 * A049855 A064339 A174010
Adjacent sequences: A019457 A019458 A019459 * A019461 A019462 A019463
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KEYWORD
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nonn,easy
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AUTHOR
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N. J. A. Sloane.
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EXTENSIONS
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Added one more term and the Mathematica coding - Robert G. Wilson v, Jul 21 2009
Formula provided by Nathaniel Johnston, Nov 11 2010
Double-checked formula and added PARI code - M. F. Hasler, Nov 12 2010
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STATUS
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approved
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