A139151
a(n) = (n!+4)/4.
Original entry on oeis.org
7, 31, 181, 1261, 10081, 90721, 907201, 9979201, 119750401, 1556755201, 21794572801, 326918592001, 5230697472001, 88921857024001, 1600593426432001, 30411275102208001, 608225502044160001, 12772735542927360001
Offset: 4
A139149
a(n) = (n!+2)/2.
Original entry on oeis.org
2, 4, 13, 61, 361, 2521, 20161, 181441, 1814401, 19958401, 239500801, 3113510401, 43589145601, 653837184001, 10461394944001, 177843714048001, 3201186852864001, 60822550204416001, 1216451004088320001, 25545471085854720001, 562000363888803840001
Offset: 2
(1!+2)/2 = 3/2 is not an integer.
a(2) = (2!+2)/2 = 2.
Offsets for above sequences are Kempner numbers
A002034.
For smallest number of the form (m!+n)/n see
A139148.
Cf.
A007749,
A020458,
A082672,
A089085,
A089130,
A117141,
A137390,
A139056-
A139066,
A139068,
A139070-
A139075,
A139157,
A139159-
A139162.
A089131
Primes of the form (k! + 3)/3.
Original entry on oeis.org
3, 41, 241, 13441, 13305601, 118562476032001, 8617338912961658880001, 123997775596633739155999816050278400000001
Offset: 1
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[a: n in [1..50] | IsPrime(a) where a is (Factorial(n)+3) div 3]; // Vincenzo Librandi, Dec 12 2011
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Select[Table[(n!+3)/3,{n,0,50}],PrimeQ] (* Vincenzo Librandi, Dec 12 2011 *)
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nfactp2d2(n) = { for(x=1,n, y=floor((x!+ 3)/3); if(isprime(y),print1(y",")) ) }
Showing 1-3 of 3 results.
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