The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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: 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

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