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Search: id:A071241
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| A071241 |
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Arithmetic mean of k and R(k) where k is a number using all even digits and R(k) is its digit reversal (A004086). |
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+0
3
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| 0, 2, 4, 6, 8, 11, 22, 33, 44, 55, 22, 33, 44, 55, 66, 33, 44, 55, 66, 77, 44, 55, 66, 77, 88, 1101, 202, 303, 404, 505, 121, 222, 323, 424, 525, 141, 242, 343, 444, 545, 161, 262, 363, 464, 565, 181, 282, 383, 484, 585, 202, 303, 404, 505, 606, 222, 323, 424, 525
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Conjecture: 101 is the largest prime member, the only other primes being 2 and 11.
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FORMULA
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{ k + R(k)}/2 where k uses only odd digits 2, 4, 6, 8 and 0.
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MAPLE
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reversal := proc(n) local i, len, new, temp: new := 0: temp := n: len := floor(log[10](n+.1))+1: for i from 1 to len do new := new+irem(temp, 10)*10^(len-i): temp := floor(temp/10): od: RETURN(new): end: alleven := proc(n) local i, flag, len, temp: temp := n: flag := 1: if n=0 then flag := 0 fi: len := floor(log[10](n+.1))+1: for i from 1 to len do if irem(temp, 10) mod 2 = 0 then temp := floor(temp/10) else flag := 0 fi: od: RETURN(flag): end: for n from 0 to 500 by 2 do if alleven(n) = 1 then printf(`%d, `, (n+reversal(n))/2) fi: od:
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CROSSREFS
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Cf. A071240, A071242.
Sequence in context: A039823 A079972 A164144 this_sequence A068062 A088169 A061563
Adjacent sequences: A071238 A071239 A071240 this_sequence A071242 A071243 A071244
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KEYWORD
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base,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), May 20 2002
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EXTENSIONS
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More terms and Maple code from James A. Sellers (sellersj(AT)math.psu.edu), May 28, 2002
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