A085864 a(1) = 2, a(n+1) = a(n)*{tau(a(n))}.

2, 4, 12, 72, 864, 20736, 933120, 117573120, 42326323200, 36315985305600, 146426052752179200, 1475974611741966336000, 37784950060594338201600000, 2031318915257551621718016000000, 212719716805770805826310635520000000

Offset

1,1

Comments

a(1) = 1, a(n+1) = a(n) + tau(a(n)) gives A064491.

Links

Table of n, a(n) for n=1..15.

Example

a(4) = 72 and tau(72)= 12, hence a(5) = 72*12= 864.

Mathematica

NestList[# DivisorSigma[0, #]&, 2, 20] (* Harvey P. Dale, Apr 23 2023 *)

Prog

(PARI) for(n=1, 16, if(n==1, a=2, a*=numdiv(a)); print(a); )

Crossrefs

Cf. A064491.

Sequence in context: A172165 A078919 A372994 * A060935 A141522 A114903

Adjacent sequences: A085861 A085862 A085863 * A085865 A085866 A085867

Keyword

nonn

Author

Amarnath Murthy, Jul 06 2003

Extensions

More terms from Ray Chandler, Jul 16 2003

Status

approved