login
a(n) = gcd(Sum_{k=1..n} c(k), Product_{j=1..n} c(j)), where c(k) is the k-th composite.
0

%I #11 Aug 02 2019 20:07:09

%S 4,2,6,27,1,1,63,6,2,112,12,9,175,1,224,250,1,5,5,1,400,14,7,5,3,6,2,

%T 8,12,3,17,847,896,22,1,1,1,6,2,1,3,3,1,2,6,31,1,1,26,4,28,2,1,1,10,

%U 2368,2448,9,7,2695,20,2,1,1,31,18,2,1,9,3596,52,10,1,1,1,5,4300,2,74,4624

%N a(n) = gcd(Sum_{k=1..n} c(k), Product_{j=1..n} c(j)), where c(k) is the k-th composite.

%e The first 8 composites are 4,6,8,9,10,12,14,15. 4+6+8+9+10+12+14+15 = 78 = 2*3*13. So a(8) = gcd(2*3*13, 4*6*8*9*10*12*14*15) = 6.

%Y Cf. A053767, A036691.

%K nonn

%O 1,1

%A _Leroy Quet_, Nov 22 2007

%E More terms from _R. J. Mathar_, Jan 13 2008