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A225091
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The odd part of the digit sum of 7^n.
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2
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1, 7, 13, 5, 7, 11, 7, 25, 31, 7, 43, 49, 37, 13, 29, 1, 13, 29, 73, 79, 19, 41, 97, 85, 73, 97, 7, 91, 133, 121, 59, 115, 103, 127, 71, 157, 17, 115, 65, 17, 71, 37, 17, 169, 175, 163, 187, 175, 17, 89, 23, 217, 49, 55, 217, 107, 211, 181, 241, 211, 199, 205
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OFFSET
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0,2
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COMMENTS
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Conjecture: the sequence contains all primes > 3.
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LINKS
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FORMULA
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MAPLE
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read(transforms) :
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MATHEMATICA
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Map[#/(2^IntegerExponent[#, 2])&[Total[IntegerDigits[7^#]]]&, Range[0, 99]] (* Peter J. C. Moses, Apr 27 2013 *)
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PROG
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(PARI) a(n) = my(s = sumdigits(7^n)); s >> valuation(s, 2); \\ Michel Marcus, Dec 19 2018
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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