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A048985 Working in base 2, replace n with the concatenation of its prime divisors in increasing order (write answer in base 10). 10
1, 2, 3, 10, 5, 11, 7, 42, 15, 21, 11, 43, 13, 23, 29, 170, 17, 47, 19, 85, 31, 43, 23, 171, 45, 45, 63, 87, 29, 93, 31, 682, 59, 81, 47, 175, 37, 83, 61, 341, 41, 95, 43, 171, 125, 87, 47, 683, 63, 173, 113, 173, 53, 191, 91, 343, 115, 93, 59, 349, 61, 95, 127, 2730 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
Patrick De Geest, Home Primes
EXAMPLE
15 = 3*5 -> 11.101 -> 11101 = 29, so a(15) = 29.
MATHEMATICA
f[n_] := FromDigits[ Flatten[ IntegerDigits[ Flatten[ Table[ #1, {#2}] & @@@ FactorInteger@n], 2]], 2]; Array[f, 64] (* Robert G. Wilson v, Jun 02 2010 *)
PROG
(Haskell)
-- import Data.List (unfoldr)
a048985 = foldr (\d v -> 2 * v + d) 0 . concatMap
(unfoldr (\x -> if x == 0 then Nothing else Just $ swap $ divMod x 2))
. reverse . a027746_row
-- Reinhard Zumkeller, Jul 16 2012
(Python)
from sympy import factorint
def a(n):
if n == 1: return 1
return int("".join(bin(p)[2:]*e for p, e in factorint(n).items()), 2)
print([a(n) for n in range(1, 65)]) # Michael S. Branicky, Oct 07 2022
CROSSREFS
Cf. A193652, A029744 (record values and where they occur).
Cf. A027746.
Sequence in context: A216937 A351629 A230625 * A337183 A348058 A112417
KEYWORD
nonn,easy,nice,base,look
AUTHOR
EXTENSIONS
More terms from Sam Alexander (pink2001x(AT)hotmail.com) and Michel ten Voorde
STATUS
approved

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Last modified June 14 14:31 EDT 2024. Contains 373400 sequences. (Running on oeis4.)