The OEIS is supported by the many generous donors to the OEIS Foundation.

Number of numbers between 1 and n-1 inclusive that are coprime to n(n+1)(n+2)(n+3).

1

`%I #14 Nov 24 2016 09:38:18
`

`%S 0,1,1,1,1,2,1,2,2,2,2,2,2,3,4,5,4,4,3,4,5,5,5,6,5,7,6,6,7,7,8,6,6,7,
`

`%T 7,10,7,8,8,9,10,9,9,10,11,12,11,11,10,12,15,12,11,11,10,14,13,14,14,
`

`%U 13,16,13,13,15,14,18,13,14,15,16,22,18,17,15,15
`

`%N Number of numbers between 1 and n-1 inclusive that are coprime to n(n+1)(n+2)(n+3).
`

`%C Which integers occur? For example, 19 does not.
`

`%H Matthew House, <a href="/A078641/b078641.txt">Table of n, a(n) for n = 1..10000</a>
`

`%e a(10) = 2 as only 1 and 7 are coprime to 10*11*12*13.
`

`%t Table[Count[Range[n - 1], k_ /; CoprimeQ[k, Pochhammer[n, 4]]], {n, 75}] (* _Michael De Vlieger_, Nov 23 2016 *)
`

`%o (PARI) newphi(v)=local(vl,fl,np); vl=length(v); np=0; for (s=1,v[1],fl=false; for (r=1,vl,if (gcd(s,v[r])>1,fl=true; break)); if (fl==false,np++)); np v=vector(4); for (i=1,50,v[1]=i; v[2]=i+1; v[3]=i+2; v[4]=i+3; print1(newphi(v)","))
`

`%K nonn
`

`%O 1,6
`

`%A _Jon Perry_, Dec 12 2002
`

`%E a(1) corrected by _Matthew House_, Nov 23 2016
`