A066123 - OEIS

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A066123

In base 2, two 'Reverse and Add' steps are needed to reach a palindrome.

11, 13, 23, 29, 39, 43, 53, 55, 57, 59, 69, 79, 81, 87, 91, 109, 117, 121, 133, 143, 151, 161, 167, 171, 173, 175, 179, 181, 183, 205, 207, 213, 215, 229, 233, 235, 237, 239, 241, 243, 245, 247, 261, 265, 277, 287, 289, 303, 311, 321, 327, 337, 343, 347, 349

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

The analog of A065207 in base 2. The number of steps starts at 0, so palindromes (cf. A006995) are excluded.

LINKS

Harry J. Smith, Table of n, a(n) for n=1,...,1000

Index entries for sequences related to Reverse and Add!

PROG

(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

CROSSREFS

Cf. A006995, A065207, A066122.

Sequence in context: A019406 A289688 A080790 * A370011 A048393 A136058

Adjacent sequences: A066120 A066121 A066122 * A066124 A066125 A066126

KEYWORD

base,nonn

AUTHOR

Klaus Brockhaus, Dec 08 2001

EXTENSIONS

OFFSET changed from 0,1 to 1,1 by Harry J. Smith, Feb 01 2010

STATUS

approved