OFFSET
0,2
COMMENTS
Freeman Dyson believes that A014963(a(n)) <> 5 is true but cannot be proved, see link. - Reinhard Zumkeller, Jan 05 2005
LINKS
T. D. Noe, Table of n, a(n) for n = 0..1000
Edge Foundation, Annual Question 2005
Richard Lipton, More on testing Dyson's conjecture (2014)
N. J. A. Sloane, Exciting Number Sequences (video of talk), Mar 05 2021.
FORMULA
MAPLE
a:= n-> (s-> parse(cat(s[-i]$i=1..length(s))))(""||(2^n)):
seq(a(n), n=0..50); # Alois P. Heinz, Jan 21 2020
MATHEMATICA
Table[FromDigits[Reverse[IntegerDigits[2^n]]], {n, 0, 35}] (* Vincenzo Librandi, Jan 22 2020 *)
PROG
(Haskell)
a004094 = a004086 . a000079 -- Reinhard Zumkeller, Apr 02 2014
(PARI) rev(n)=subst(Polrev(digits(n)), 'x, 10)
a(n)=rev(2^n) \\ Charles R Greathouse IV, Oct 20 2014
(PARI) apply( {A004094(n)=fromdigits(Vecrev(digits(2^n)))}, [0..44]) \\ M. F. Hasler, Feb 18 2021
(Magma) [Seqint(Reverse(Intseq(2^n))): n in [0..35]]; // Vincenzo Librandi, Jan 22 2020
(Python)
def A004094(n):
return int(str(2**n)[::-1]) # Chai Wah Wu, Feb 19 2021
CROSSREFS
The following are parallel families: A000079 (2^n), A004094 (2^n reversed), A028909 (2^n sorted up), A028910 (2^n sorted down), A036447 (double and reverse), A057615 (double and sort up), A263451 (double and sort down); A000244 (3^n), A004167 (3^n reversed), A321540 (3^n sorted up), A321539 (3^n sorted down), A163632 (triple and reverse), A321542 (triple and sort up), A321541 (triple and sort down).
Cf. A004086 (read n backwards).
For indices of primes see A057708.
KEYWORD
nonn,base,easy,changed
AUTHOR
EXTENSIONS
More terms from Reinhard Zumkeller, Jan 05 2005
STATUS
approved