

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



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)


CROSSREFS



KEYWORD

nonn


AUTHOR



EXTENSIONS



STATUS

approved



