|
%I #39 Jun 06 2017 03:01:57
%S 1,1,3,5,7,9,62,105,4612,477839,5221660,120695273,
%T 13517914794489425446,949763730038903507583,
%U 805993247839619614799176726719363512,2572332284084802308827712032135882716710570503279953274299454873
%N a(1) = a(2) = 1; a(n) = a(n-1) + gpf(1 + Product_{k = 1..n - 2} a(k)), where gpf means "greatest prime factor" (A006530).
%e a(3) = a(2) + gpf(1 + a(1)) = 1 + gpf(1 + 1) = 1 + 2 = 3.
%e a(4) = a(3) + gpf(1 + a(1) * a(2)) = 3 + gpf(1 + 1 * 1) = 3 + 2 = 5.
%e a(5) = a(4) + gpf(1 + a(1) * a(2) * a(3)) = 5 + gpf(1 + 1 * 1 * 3) = 5 + 2 = 7.
%o (PARI) gpf(n)=my(f=factor(n)[, 1]); f[#f];
%o a(n)=if(n>2, a(n-1)+gpf(1+prod(i=1, n-2, a(i))), 1)
%o first(m)=my(v=vector(m)); v[1]=1; v[2]=1; for(i=3, m, v[i]=v[i-1]+gpf(1+prod(k=1, i-2, v[k]))); v
%Y Cf. A006530, A078695.
%K nonn
%O 1,3
%A _Anders Hellström_, Nov 22 2015
|
