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 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: A305857 A014627 A145781 * A215659 A028688 A030753 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

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Last modified September 26 16:43 EDT 2020. Contains 337374 sequences. (Running on oeis4.)