A078641 Number of numbers between 1 and n-1 inclusive that are coprime to n(n+1)(n+2)(n+3).

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, 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, 13, 16, 13, 13, 15, 14, 18, 13, 14, 15, 16, 22, 18, 17, 15, 15

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

Sequence in context: A029404 A029417 A029237 * A072628 A343901 A193386

Adjacent sequences: A078638 A078639 A078640 * A078642 A078643 A078644

Keyword

nonn

Author

Jon Perry, Dec 12 2002

Extensions

a(1) corrected by Matthew House, Nov 23 2016

Status

approved