A054251 a(0) = 1; a(n) = Sum_{0 <= k < n and gcd(k, n) != 1} a(k).

1, 0, 1, 1, 2, 1, 5, 1, 9, 7, 19, 1, 45, 1, 83, 79, 165, 1, 417, 1, 827, 639, 1575, 1, 3875, 927, 7025, 5069, 14689, 1, 35461, 1, 64199, 47175, 128399, 52727, 309767, 1, 566565, 409567, 1186863, 1, 2835257, 1, 5202425, 4888729, 10357675, 1, 26066615

Offset: 0

Author

David W. Wilson

Keywords

• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 0..1000

Crossrefs

Cf. A045545.

Programs

Mathematica

a[0]:= 1; a[n_]:= a[n] =Sum[If[GCD[k, n]!=1, a[k], 0], {k,0,n-1}];
Table[a[n], {n, 0, 50}] (* G. C. Greubel, Jul 31 2019 *)

PARI

a(n) = if(n==0, 1, sum(j=0,n-1, if(gcd(j,n)!=1, a(j), 0)));
vector(50, n, n--; a(n)) \\ G. C. Greubel, Jul 31 2019