OFFSET
1,1
COMMENTS
The product of a pair of consecutive refactorable numbers is itself refactorable.
LINKS
S. Colton, Refactorable Numbers - A Machine Invention, J. Integer Sequences, Vol. 2, 1999, #2.
FORMULA
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
KEYWORD
nonn
AUTHOR
Simon Colton (simonco(AT)cs.york.ac.uk)
STATUS
approved