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

1,1

Comments

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

Links

Table of n, a(n) for n=1..17.

S. Colton, Refactorable Numbers - A Machine Invention, J. Integer Sequences, Vol. 2, 1999, #2.

S. Colton, HR - Automatic Theory Formation in Pure Mathematics

Formula

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

Example

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

Prog

(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

Crossrefs

Cf. A033950.

Sequence in context: A079478 A367492 A221709 * A324566 A276518 A297410

Adjacent sequences: A036896 A036897 A036898 * A036900 A036901 A036902

Keyword

nonn

Author

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

Status

approved