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A080689
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Powers of 10 that reach ...,7,8,4,2,1 under the mapping: if n is even divide by 2 else add 1.
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0
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2, 5, 18, 21, 24, 27, 30, 33, 36, 49, 52, 55, 58, 61, 64, 77, 80, 83, 86, 89, 92, 105, 108, 111, 114, 117, 120, 123, 136, 139, 142, 145, 148, 151, 164, 167, 170, 173, 176, 179, 182, 195, 198, 201, 204, 207, 210, 223, 226, 229, 232, 235, 238, 251, 254, 257, 260
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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PROG
| (PARI) xnp10(n, p) = { for(x=1, n, p10 = 10^x; while(p10>1, if(p10%2==0, p10/=2, p10 = p10*p+1; ); if(p10==7, print1(x" ")) ) ) }
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CROSSREFS
| Cf. A022803.
Sequence in context: A124374 A113617 A117839 * A026321 A048221 A183365
Adjacent sequences: A080686 A080687 A080688 * A080690 A080691 A080692
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KEYWORD
| easy,nonn
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AUTHOR
| Cino Hilliard (hillcino368(AT)gmail.com), Mar 23 2003
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