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Search: id:A067227
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| A067227 |
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n is prime and remains prime when its leading digit is replaced by any nonzero digit that is a power of 2 (i.e. 2, 4, 8). |
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+0
1
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| 13, 23, 43, 53, 73, 83, 139, 157, 163, 239, 257, 263, 439, 457, 463, 557, 563, 739, 757, 839, 857, 863, 1297, 1423, 1447, 1663, 1861, 1999, 2111, 2243, 2273, 2297, 2423, 2447, 2663, 2861, 2969, 2999, 4111, 4243, 4273, 4297, 4423, 4447, 4663, 4861, 4969
(list; graph; listen)
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OFFSET
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0,1
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EXAMPLE
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53 is prime and so are 23, 43, 83, so 53 is a term of the sequence.
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MATHEMATICA
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(*replaces the leading digit of n by m*) f[n_, m_] := FromDigits[Flatten[Append[IntegerDigits[m], Drop[IntegerDigits[n], 1]]]]; Select[Range[10^4], PrimeQ[ # ] && PrimeQ[f[ #, 2]] && PrimeQ[f[ #, 4]] && PrimeQ[f[ #, 8]] & ]
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CROSSREFS
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Sequence in context: A119488 A165350 A112394 this_sequence A068712 A103166 A154863
Adjacent sequences: A067224 A067225 A067226 this_sequence A067228 A067229 A067230
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KEYWORD
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base,nonn
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AUTHOR
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Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Feb 20 2002
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