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A065217
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Twelve 'Reverse and Add' steps are needed to reach a palindrome.
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3
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2069, 2159, 2249, 2339, 2429, 2519, 2609, 2699, 2789, 2879, 2969, 3068, 3158, 3248, 3338, 3428, 3518, 3608, 3698, 3788, 3878, 3968, 4067, 4157, 4247, 4337, 4427, 4517, 4607, 4697, 4787, 4877, 4967, 5066, 5156, 5246, 5336, 5426, 5516, 5606, 5696, 5786
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| The number of steps starts at 0, so palindromes (cf. A002113) are excluded. This sequence coincides with the corresponding sequence not excluding palindromes (A015993) for the entries shown in the database. The first divergence occurs at 10901.
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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); 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) } { n=0; for (m = 0, 10^9, p=m; b=1; for (i=1, 12, if (Palin(p), b=0; break); p=Rev(p) + p); if (b && Palin(p), write("b065217.txt", n++, " ", m); if (n==1000, return)) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Oct 14 2009]
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CROSSREFS
| A002113, A015993, A065206.
Sequence in context: A204310 A168432 A015993 * A200829 A035871 A062913
Adjacent sequences: A065214 A065215 A065216 * A065218 A065219 A065220
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KEYWORD
| nonn,base
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AUTHOR
| Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Oct 21 2001
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EXTENSIONS
| OFFSET changed from 0,1 to 1,1 by Harry J. Smith (hjsmithh(AT)sbcglobal.net), Oct 14 2009
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