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 A166342 Numbers n such that (n+2)*n!*Sum((-1)^k/k!),k=0..n+2 is prime. 0
 2, 3, 4, 8, 13, 42, 64, 166, 573, 1711 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS No further terms up to n=20000. The sequence a[n]=(n+2)*n!*Sum((-1)^k/k!),k=0..n+2 is A000255. LINKS FORMULA n is an index of the sequence a[n]=(n+2)*n!*Sum((-1)^k/k!),k=0..n+2 such that a[n] is prime. EXAMPLE For n=3, a[3]=11 which is prime. PROG (PARI) z_even=1; z_odd=1; for(n=1, 20000, if(n%2==1, z_odd=(n+2)*(n-1)*z_odd+1; if((ispseudoprime(z_odd)), print(n="n)), z_even=(n+2)*(n-1)*z_even-1; if((ispseudoprime(z_odd)), print(n="n))); ); CROSSREFS Cf. A000255 (corresponding sequence). Sequence in context: A186272 A092075 A091415 * A091816 A266400 A274914 Adjacent sequences:  A166339 A166340 A166341 * A166343 A166344 A166345 KEYWORD nonn AUTHOR Mike Oakes, Oct 12 2009 STATUS approved

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Last modified May 16 15:56 EDT 2022. Contains 353706 sequences. (Running on oeis4.)