A120938 - OEIS

%I #11 Aug 09 2015 14:47:52

%S 1,2,3,5,10,13,26,52,65,130,143,273,416,426,569,1138,1707,3414,3983,

%T 7966,11949,13087,26174,38123,76246,152492,190615,381230,571845,

%U 1143690,1181813,2325503,4651006,9302012,11627515,20929527,32557042,65114084

%N a(0)=1. a(n) = a(n-1) + (largest integer occurring among {a(0),a(1),a(2),...,a(n-1)} that is coprime to n).

%e Among the terms {a(0),a(1),a(2),a(3),a(4),a(5)}, a(5) = 13 is the largest term that is coprime to 6. So a(6) = a(5) + 13 = 26.

%p A120938 := proc(nmax) local a,cpr,n,i; a := [1,2]; for n from 3 to nmax do cpr := 0; for i from 1 to n-1 do if gcd(n-1,a[i]) = 1 and a[i] > cpr then cpr := a[i]; fi; od; a := [op(a), a[n-1]+cpr]; od: RETURN(a); end: nmax := 100 : a := A120938(nmax) : for n from 1 to nops(a) do printf("%d,",a[n]); od; # _R. J. Mathar_, Aug 17 2006

%o (PARI) {m=37;print1(a=1,",");v=[a];for(n=1,m,a=0;for(j=1,n,if(gcd(v[j],n)==1&&a<v[j],a=v[j]));print1(a=a+v[n],",");v=concat(v,a))} \\ _Klaus Brockhaus_, Aug 16 2006

%Y Cf. A120939.

%K nonn

%O 0,2

%A _Leroy Quet_, Jul 17 2006

%E More terms from _Klaus Brockhaus_, Aug 16 2006

%E More terms from _R. J. Mathar_, Aug 17 2006