0,1

Sequence A058042 written in base 10. 22 is the smallest number whose base 2 trajectory does not contain a palindrome.

lim_{n -> infinity} a(n)/a(n-1) = 2 for n mod 2 = 0.

lim_{n -> infinity} a(n)/a(n-1) = 1 for n mod 2 = 1. - Klaus Brockhaus, Dec 09 2009

T. D. Noe, Table of n, a(n) for n=0..500

Klaus Brockhaus, On the 'Reverse and Add!' algorithm in base 2

Index entries for linear recurrences with constant coefficients, signature (0,3,0,0,0,-6,0,4).

a(0) = 22; a(1) = 35; for n > 1 and n = 2 (mod 4): a(n) = 6*2^(2*k)-3*2^k where k = (n+6)/4; n = 3 (mod 4): a(n) = 6*2^(2*k)+3*2^k-3 where k = (n+5)/4; n = 0 (mod 4): a(n) = 12*2^(2*k)-3*2^k where k = (n+4)/4; n = 1 (mod 4): a(n) = 12*2^(2*k)+9*2^k-3 where k = (n+3)/4. - Klaus Brockhaus, Sep 05 2002

G.f.: (22+35*x+18*x^2-72*x^4-90*x^5-48*x^6-60*x^7+80*x^8+112*x^9) / ((1-x)*(1+x)*(1-2*x^2)*(1-2*x^4)). - Klaus Brockhaus, Sep 05 2002, edited Dec 09 2009

a(n+1) = A055944(a(n)). - Reinhard Zumkeller, Apr 21 2013

binRA[n_] := If[Reverse[IntegerDigits[n, 2]] == IntegerDigits[n, 2], n, FromDigits[Reverse[IntegerDigits[n, 2]], 2] + n]; NestList[binRA, 22, 100] (* Adapted from Ben Branman's code for A213012, Alonso del Arte, Jun 02 2012 *)

(ARIBAS) m := 22; stop := 36; c := 0; while c < stop do write(m, ", "); k := bit_length(m); rev := 0; for i := 0 to k-1 do if bit_test(m, i) then rev := bit_set(rev, k-1-i); end; end; inc(c); m := m+rev; end; .

(PARI) {m=22; stop=36; c=0; while(c<stop, print1(k=m, ", "); rev=0; while(k>0, d=divrem(k, 2); k=d[1]; rev=2*rev+d[2]); c++; m=m+rev)}

(Magma) trajectory:=function(init, steps, base) a:=init; S:=[a]; for n in [1..steps] do a+:=Seqint(Reverse(Intseq(a, base)), base); Append(~S, a); end for; return S; end function; trajectory(22, 35, 2); // Klaus Brockhaus, Dec 09 2009

(Haskell)

a061561 n = a061561_list !! n

a061561_list = iterate a055944 22 -- Reinhard Zumkeller, Apr 21 2013

Cf. A035522 (trajectory of 1 in base 2), A058042 (trajectory of 22 in base 2, written in base 2), A075253 (trajectory of 77 in base 2), A075268 (trajectory of 442 in base 2), A077076 (trajectory of 537 in base 2), A077077 (trajectory of 775 in base 2), A066059 (trajectory of n in base 2 (presumably) does not reach a palindrome), A075252 (trajectory of n in base 2 does not reach a palindrome and (presumably) does not join the trajectory of any term m < n), A075153 (trajectory of 318 in base 4).

Cf. A171470 (a(4*n)/2), A171471 (a(4*n+1)), A171472 (a(4*n+2)/12), A171473 (a(4*n+3)/3).

Sequence in context: A159518 A245365 A100039 * A233404 A167277 A084141

Adjacent sequences: A061558 A061559 A061560 * A061562 A061563 A061564

nonn,base

N. J. A. Sloane, May 18 2001

More terms from Klaus Brockhaus, May 27 2001

approved