A135324 - OEIS

%I #11 Sep 18 2015 03:50:42

%S 1,1,5,7,30,11,91,50,120,64,385,76,650,191,354,372,1496,243,2109,468,

%T 1081,795,3795,560,3450,1336,3033,1432,7714,692,9455,2856,4595,3056,

%U 6974,1836,16206,4299,7766,3576,22140,2126,25585,6100,8922,7711,33511

%N a(n) = Sum_{k=1..phi(n)} k*t(k), where t(k) is the k-th positive integer which is coprime to n and phi(n) is the number of positive integers which are <= n and are coprime to n.

%F a(n) = Sum_{k=1..A000010(n)} k*A126572(n,k). - _R. J. Mathar_, Jan 30 2008

%e The positive integers that are coprime to 12 and are <= 12 are 1,5,7,11. So a(12) = 1*1 + 2*5 + 3*7 + 4*11 = 1+10+21+44 =76.

%p A126572 := proc(n,k) local a,i ; a := 1 ; for i from 1 to k do if i = k then RETURN(a) ; fi ; a := a+1 ; while gcd(a,n) <> 1 do a := a+1 ; od; od: end: A135324 := proc(n) add( k*A126572(n,k),k=1..numtheory[phi](n)) ; end: for n from 1 to 80 do printf("%d, ",A135324(n) ) ; od: # _R. J. Mathar_, Jan 30 2008

%K nonn

%O 1,3

%A _Leroy Quet_, Dec 06 2007

%E More terms from _R. J. Mathar_, Jan 30 2008