

A109162


a(1) = 1; for n > 1, a(n) = A019565(a(n1)).


5




OFFSET

1,2


COMMENTS

After the initial 1, evenindexed terms are of the form 4k+2 (members of A016825) and oddindexed terms are of the form 6k+3 (members of A016945). However, not all even terms after 2 are multiples of three, because not all oddindexed 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 AdamsWatters, 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 memoizationmacro 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. AdamsWatters, Aug 29 2006


STATUS

approved



