A030103 Base 4 reversal of n (written in base 10).

0, 1, 2, 3, 1, 5, 9, 13, 2, 6, 10, 14, 3, 7, 11, 15, 1, 17, 33, 49, 5, 21, 37, 53, 9, 25, 41, 57, 13, 29, 45, 61, 2, 18, 34, 50, 6, 22, 38, 54, 10, 26, 42, 58, 14, 30, 46, 62, 3, 19, 35, 51, 7, 23, 39, 55, 11, 27, 43, 59, 15, 31, 47, 63, 1, 65, 129, 193, 17, 81, 145, 209, 33, 97, 161

Offset

0,3

Links

Reinhard Zumkeller, Table of n, a(n) for n = 0..10000

Prog

(Haskell)
import Data.List (unfoldr)
a030103 n = foldl (\v d -> 4*v + d) 0 $ unfoldr dig n where
    dig x = if x == 0 then Nothing else Just $ swap $ divMod x 4
-- Reinhard Zumkeller, Oct 10 2011
(PARI) a(n, b=4)=subst(Polrev(base(n, b)), x, b)) /* where */
base(n, b)={my(a=[n%b]); while(0<n\=b, a=concat(n%b, a)); a}  \\ - M. F. Hasler, Nov 04 2011
(MIT/GNU Scheme)
(define (A030103 n) (if (zero? n) n (let ((uplim (+ (A000523 n) (- 1 (modulo (A000523 n) 2))))) (add (lambda (i) (* (bit_i n (+ i (expt -1 i))) (expt 2 (- uplim i)))) 0 uplim))))
(define (bit_i n i) (modulo (floor->exact (/ n (expt 2 i))) 2))
;; The functional add implements sum_{i=lowlim..uplim} intfun(i):
(define (add intfun lowlim uplim) (let sumloop ((i lowlim) (res 0)) (cond ((> i uplim) res) (else (sumloop (1+ i) (+ res (intfun i)))))))
;; Antti Karttunen, Oct 30 2013

Crossrefs

Cf. A004086, A030101 - A030108, A048703, A055948, A035524.

Sequence in context: A011357 A080409 A255689 * A255589 A290053 A105640

Adjacent sequences: A030100 A030101 A030102 * A030104 A030105 A030106

Keyword

nonn,base,look

Author

David W. Wilson

Status

approved