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A119497
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Primes of the form n! + n!! + 1.
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0
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OFFSET
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1,1
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REFERENCES
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G. Balzarotti and P. P. Lava, Le sequenze di numeri interi, Hoepli, 2008, p. 159.
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LINKS
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EXAMPLE
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For n=2, 2! + 2!! + 1 = 2 + 2 + 1 = 5, which is prime.
For n=6, 6! + 6!! + 1 = 720 + 48 + 1 = 769, which is prime.
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MAPLE
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SFACT:= proc(n) local i, j, k; for k from 1 by 1 to n do i:=k; j:=k-2; while j >0 do i:=i*j; j:=j-2; od: if isprime(k!+i+1) then print(k!+i+1); fi; od: end: SFACT(300);
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PROG
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(PARI) dfac(n)=prod(k=0, n\2-1, n-k-k)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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