A048985 Working in base 2, replace n with the concatenation of its prime divisors in increasing order (write answer in base 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

Offset

1,2

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

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. A037276, A048986, A064841.

Cf. A193652, A029744 (record values and where they occur).

Cf. A027746.

Sequence in context: A216937 A351629 A230625 * A337183 A348058 A112417

Adjacent sequences: A048982 A048983 A048984 * A048986 A048987 A048988

Keyword

nonn,easy,nice,base,look

Author

N. J. A. Sloane

Extensions

More terms from Sam Alexander (pink2001x(AT)hotmail.com) and Michel ten Voorde

Status

approved