OFFSET
1,2
COMMENTS
A natural number n occurs here if and only if it is either a power of 2, or satisfies A001511(n) = A071178(n) [the exponent of highest power of 2 dividing n is one less than the exponent of the largest prime factor of n], and all the intermediate exponents form a palindrome. [Please see the definition of A241916.]
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..4931
FORMULA
a(n) = A242418(n+1)/2.
EXAMPLE
MATHEMATICA
f[n_] := If[n == 1, {0}, Function[f, ReplacePart[Table[0, {PrimePi[f[[-1, 1]]]}], #] &@ Map[PrimePi@ First@ # -> Last@ # &, f]]@ FactorInteger@ n]; g[w_List] := Times @@ Flatten@ MapIndexed[Prime[#2]^#1 &, w]; Table[#[[n + 1]]/2, {n, Length@ # - 1}] &@ Select[Range@ 400, g@ f@ # == g@ Reverse@ f@ # &] (* Michael De Vlieger, Aug 27 2016 *)
PROG
(Scheme, with Antti Karttunen's IntSeq-library)
;; Alternatively:
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, May 03 2014
STATUS
approved