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A066123
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In base 2, two 'Reverse and Add' steps are needed to reach a palindrome.
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1
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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; internal format)
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OFFSET
| 1,1
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COMMENTS
| The analogue of A065207 in base 2. The number of steps starts at 0, so palindromes (cf. A006995) are excluded.
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LINKS
| Harry J. Smith, Table of n, a(n) for n=1,...,1000
Index entries for sequences related to Reverse and Add!
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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)) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Feb 01 2010]
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CROSSREFS
| A006995, A065207, A066122.
Sequence in context: A075519 A019406 A080790 * A048393 A136058 A106073
Adjacent sequences: A066120 A066121 A066122 * A066124 A066125 A066126
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KEYWORD
| base,nonn
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AUTHOR
| Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Dec 08 2001
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EXTENSIONS
| OFFSET changed from 0,1 to 1,1 by Harry J. Smith (hjsmithh(AT)sbcglobal.net), Feb 01 2010
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