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A085747
Least positive k such that n! + k is a semiprime.
7
3, 2, 3, 1, 1, 1, 1, 1, 5, 1, 3, 17, 1, 1, 7, 2, 3, 23, 1, 1, 11, 29, 3, 1, 1, 1, 37, 1, 41, 2, 19, 11, 11, 1, 7, 3, 41, 1, 13, 127, 47, 59, 2, 37, 5, 37, 59, 1, 2, 73, 59, 79, 73, 1, 1, 61, 118, 37, 1, 61, 31, 37, 43, 7, 83, 71, 19, 7, 103, 19, 1, 107, 37, 167, 1, 103, 3, 73, 109, 97
OFFSET
1,1
COMMENTS
a(106) >= 139. - Sean A. Irvine, Oct 29 2019
a(n) = 1 iff n in A078778.
LINKS
Max Alekseyev, Table of n, a(n) for n = 1..105 (a(100) and a(104) from Sean A. Irvine)
MATHEMATICA
Table[SelectFirst[Range@ 1000, PrimeOmega[n! + #] == 2 &], {n, 40}] (* Michael De Vlieger, Mar 08 2016, Version 10 *)
PROG
(PARI) a(n) = {k = 1; while (bigomega(n!+k) != 2, k++); k; } \\ Michel Marcus, Mar 08 2016
(Magma) m:=1; sol:=[]; for n in [1..40] do k:=1; while &+[d[2]: d in Factorization(Factorial(n)+k)] ne 2 do k:=k+1; end while; sol[m]:=k; m:=m+1; end for; sol; // Marius A. Burtea, Aug 24 2019
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Jason Earls, Jul 21 2003
EXTENSIONS
Extended by Robert G. Wilson v, Jul 27 2003
a(55) from Ray Chandler, Nov 09 2003
a(56)-a(80) from Sean A. Irvine, Mar 29 2010
STATUS
approved