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!)
 A109162 a(1) = 1; for n > 1, a(n) = A019565(a(n-1)). 5
 1, 2, 3, 6, 15, 210, 10659, 54230826, 249853434654335387610276087 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS After the initial 1, even-indexed terms are of the form 4k+2 (members of A016825) and odd-indexed terms are of the form 6k+3 (members of A016945). However, not all even terms after 2 are multiples of three, because not all odd-indexed terms are of the form 4k+3. For example, because a(11) is of the form 4k+1, a(12) cannot be a multiple of three. - Antti Karttunen, Jun 18 2017 LINKS Frank Adams-Watters, Table of n, a(n) for n = 1..11 EXAMPLE a(4) = 6, which is 110 in binary. So a(5) is the product of the primes corresponding to the 1's of 110, 3*5 = 15. MATHEMATICA NestList[Times @@ Prime@ Flatten@ Position[#, 1] &@ Reverse@ IntegerDigits[#, 2] &, 1, 11] (* Michael De Vlieger, Aug 20 2017 *) PROG (Scheme, with memoization-macro definec) (definec (A109162 n) (if (zero? n) n (A019565 (A109162 (- n 1))))) ;; Antti Karttunen, Jun 18 2017 CROSSREFS Cf. A019565, A285320 (a left inverse). The left edge of A285332 and A285333. Sequence in context: A014627 A145781 A351880 * A215659 A028688 A342027 Adjacent sequences: A109159 A109160 A109161 * A109163 A109164 A109165 KEYWORD nonn AUTHOR Leroy Quet, Aug 18 2005 EXTENSIONS More terms from Franklin T. Adams-Watters, Aug 29 2006 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 18 16:32 EDT 2024. Contains 372664 sequences. (Running on oeis4.)