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A019460
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Add 1, multiply by 1, add 2, multiply by 2, etc., start with 2.
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12
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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, 648306912009, 9724603680135, 9724603680151, 155593658882416
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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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FORMULA
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a(2n) = 2*(A000522(n) + n!) - n - 2.
Recursive: a(0) = 2, a(n) = (1 + floor((n-1)/2) - ceiling((n-1)/2))*(a(n-1) + (n+2)/2) + (ceiling((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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/* 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 }
(Python)
l=[2]
for n in range(1, 101):
l.append(l[n - 1] + ((n + 1)//2) if n%2 else l[n - 1]*(n//2))
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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Formula double-checked and PARI code added by M. F. Hasler, Nov 12 2010
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STATUS
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approved
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