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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

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: A320443 A079478 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

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Last modified May 22 14:32 EDT 2019. Contains 323480 sequences. (Running on oeis4.)