A100674 - OEIS

%I #17 Oct 26 2019 16:30:46

%S 1,1,2,3,5,9,8,9,10,13,10,27,24,59,14,80,127,17,144,169,43,21,84,183,

%T 32,126,184,140,441,124,44,74,32,209,204,463,36,617,38,798,1025,1124,

%U 62,86,105,422,46,551,774,222,157,51,476,820,1492,81,470,186,183,78,459,884

%N a(1) = 1; a(n+1) = Sum_{k=1..n} a(gcd(k, a(n))).

%H Ivan Neretin, <a href="/A100674/b100674.txt">Table of n, a(n) for n = 1..10000</a>

%p a[1]:=1: for n from 2 to 70 do b[n]:=[seq(a[gcd(k,a[n-1])],k=1..n-1)]: a[n]:=sum(b[n][j],j=1..nops(b[n])) od: seq(a[n],n=1..70);

%t a[1] = 1; a[n_] := a[n] = Plus @@ a /@ GCD[Range[n - 1], a[n - 1]]; Table[ a[n], {n, 62}] (* _Robert G. Wilson v_, Dec 09 2004 *)

%o (GAP) a:=[1];; for n in [2..65] do a[n]:=Sum([1..n-1],k->a[Gcd(k,a[n-1])]); od; a; # _Muniru A Asiru_, Oct 21 2018

%K nonn

%O 1,3

%A _Leroy Quet_, Dec 06 2004

%E More terms from _Emeric Deutsch_ and _Robert G. Wilson v_, Dec 09 2004