A085865 a(1) = 2, a(n+1) = a(n)*{sigma(a(n))}, where sigma(n) is the sum of the divisors function.

2, 6, 72, 14040, 707616000, 2299654269739008000, 25353370781704805143366427867873280000, 3361021040447648920437074194752848938805829494939344230020451929790873600000

Offset: 1

Author

Amarnath Murthy, Jul 06 2003

Keywords

• nonn

Comments

a(1) = 1, a(n+1) = a(n) + sigma(a(n)) gives A081973.

Examples

			a(3) = 72 and sigma(72)= 195, hence a(4) = 72*195 = 14040.
		

Crossrefs

Cf. A064491, A081973, A085864.

Programs

PARI

for(n=1,9,if(n==1,a=2,a*=sigma(a)); print(a); )

Extensions

More terms from Ray Chandler, Jul 16 2003