A036899 Products of pairs of consecutive refactorable numbers.

2, 72, 2311920, 2562840000, 3844062000, 10617344640, 39923436672, 49213207440, 72555078960, 215073801360, 476873804160, 719511945840, 972291644352, 1567905917760, 2012086928880, 4707721763712, 7251605387280

Offset: 1

Author

Simon Colton (simonco(AT)cs.york.ac.uk)

Keywords

• nonn

Comments

The product of a pair of consecutive refactorable numbers is itself refactorable.

Examples

			8 and 9 are consecutive refactorable numbers, so 8*9 = 72 is in the sequence.
		

Links

• S. Colton, Refactorable Numbers - A Machine Invention, J. Integer Sequences, Vol. 2, 1999, #2.
• S. Colton, HR - Automatic Theory Formation in Pure Mathematics

Crossrefs

Cf. A033950.

Programs

PARI

isrefac(n) = ! (n % numdiv(n));
lista(nn) = {for (n=1, nn, if (isrefac(n) && isrefac(n+1), print1(n*(n+1) ", ")););} \\ Michel Marcus, Aug 31 2013

Formula

a(n) = A036898(2n) * A036898(2n+1). - Michel Marcus, Aug 31 2013