%I #9 Jul 11 2015 00:08:24
%S 11,13,23,29,39,43,53,55,57,59,69,79,81,87,91,109,117,121,133,143,151,
%T 161,167,171,173,175,179,181,183,205,207,213,215,229,233,235,237,239,
%U 241,243,245,247,261,265,277,287,289,303,311,321,327,337,343,347,349
%N In base 2, two 'Reverse and Add' steps are needed to reach a palindrome.
%C The analog of A065207 in base 2. The number of steps starts at 0, so palindromes (cf. A006995) are excluded.
%H Harry J. Smith, <a href="/A066123/b066123.txt">Table of n, a(n) for n=1,...,1000</a>
%H <a href="/index/Res#RAA">Index entries for sequences related to Reverse and Add!</a>
%o (PARI) Rev(x)= { local(d, r=0); while (x>0, d=x%10; x\=10; r=r*10 + d); return(r) } digitsIn(x)= { local(d); if (x==0, return(1)); d=1 + log(x)\log(10); if (10^d == x, d++, if (10^(d-1) > x, d--)); return(d) } Palin(x)= { local(d,e,f,i,t,y); if (x==0, return(1)); y=x; d=digitsIn(x); t=10^(d - 1); for (i=1, d\2, f=y-10*(y\10); y\=10; e=x\t; x-=t*e; t/=10; if (e!=f, return(0)) ); return(1) } baseE(x, b)= { local(d, e=0, f=1); while (x>0, d=x-b*(x\b); x\=b; e+=d*f; f*=10); return(e) } baseI(x, b)= { local(d, e=0, f=1); while (x>0, d=x-10*(x\10); x\=10; e+=d*f; f*=b); return(e) } calcB(p)= { local(b,r); b=baseE(p, 2); r=Rev(b); d=baseI(r, 2) + p; b=baseE(d, 2); return(b); } { n=0; for (m=1, 10^9, d=m; t=1; b=baseE(d, 2); for (i=1, 2, if (Palin(b), t=0; break); b=calcB(d)); if (t && Palin(b), write("b066123.txt", n++, " ", m); if (n==1000, return)) ) } \\ _Harry J. Smith_, Feb 01 2010
%Y Cf. A006995, A065207, A066122.
%K base,nonn
%O 1,1
%A _Klaus Brockhaus_, Dec 08 2001
%E OFFSET changed from 0,1 to 1,1 by _Harry J. Smith_, Feb 01 2010