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A036899 Products of pairs of consecutive refactorable numbers. 0
2, 72, 2311920, 2562840000, 3844062000, 10617344640, 39923436672, 49213207440, 72555078960, 215073801360, 476873804160, 719511945840, 972291644352, 1567905917760, 2012086928880, 4707721763712, 7251605387280 (list; graph; refs; listen; history; text; internal format)
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
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
KEYWORD
nonn
AUTHOR
Simon Colton (simonco(AT)cs.york.ac.uk)
STATUS
approved

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Last modified May 25 15:42 EDT 2024. Contains 372800 sequences. (Running on oeis4.)