A132996 a(n) = gcd(Sum_{k=1..n} c(k), Product_{j=1..n} c(j)), where c(k) is the k-th composite.

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, 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, 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

Offset: 1

Author

Leroy Quet, Nov 22 2007

Keywords

• nonn

Examples

			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.
		

Crossrefs

Cf. A053767, A036691.

Programs

Mathematica

lim=80;c[n_]:=n-PrimePi[n]-1;i=0;Do[Until[c[i]==m,i++];Cmp[m]=i,{m,lim}];Table[GCD[Sum[Cmp[k],{k,n}],Product[Cmp[j],{j,n}]],{n,lim}] (* James C. McMahon, Mar 09 2025 *)

Extensions

More terms from R. J. Mathar, Jan 13 2008