OFFSET
1,6
COMMENTS
Which integers occur? For example, 19 does not.
LINKS
Matthew House, Table of n, a(n) for n = 1..10000
EXAMPLE
a(10) = 2 as only 1 and 7 are coprime to 10*11*12*13.
MATHEMATICA
Table[Count[Range[n - 1], k_ /; CoprimeQ[k, Pochhammer[n, 4]]], {n, 75}] (* Michael De Vlieger, Nov 23 2016 *)
PROG
(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)", "))
CROSSREFS
KEYWORD
nonn
AUTHOR
Jon Perry, Dec 12 2002
EXTENSIONS
a(1) corrected by Matthew House, Nov 23 2016
STATUS
approved