login
Group the prime numbers so that the sum of the terms of the n-th group is a multiple of that of the (n-1)-st group: (2), (3,5), (7,11,13,17), (19,23,29,31,37...,79,83), ...; a(n) = sum of n-th group.
3

%I #6 Dec 05 2013 19:55:58

%S 2,8,48,816,74256,2335722480,3265147014612865200

%N Group the prime numbers so that the sum of the terms of the n-th group is a multiple of that of the (n-1)-st group: (2), (3,5), (7,11,13,17), (19,23,29,31,37...,79,83), ...; a(n) = sum of n-th group.

%o (PARI) p=2; print1(s=p,","); while(s<10^9,p=nextprime(p+1); a=p; while(a%s>0,p=nextprime(p+1); a=a+p); print1(s=a,","))

%Y Cf. A079803, A079804, A079805.

%K nonn

%O 1,1

%A _Amarnath Murthy_, Feb 05 2003

%E a(5), a(6) and PARI code from _Klaus Brockhaus_, Feb 13 2003

%E a(7) from _Ryan Propper_, Aug 29 2005