1,1

a(13) <= 20541737393358731550. a(14) <= 3553720569051060558150. - Donovan Johnson, Jul 13 2011

Table of n, a(n) for n=1..12.

a(9) = 82937795850 = 2*3^2*5^2*7*13*19*37*43*67 (9 distinct prime factors). Sigma(82937795850) = 307906959360 = 2^11*3*5*7*11*13*17*19*31 (9 distinct prime factors).

Cf. A000203, A001221.

Sequence in context: A180402 A089039 A156451 * A156472 A108640 A084971

Adjacent sequences: A152614 A152615 A152616 * A152618 A152619 A152620

nonn

Donovan Johnson, Dec 13 2008

a(12) from Donovan Johnson, Jul 13 2011

approved