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A110765
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Let n in binary be a k-digit number say abbaaa... where a = 1 and b = 0. a(n) = 2^a*3^b*5^b*7*a... primes in increasing order raised to the powers starting from the MSB.
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0
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2, 2, 6, 2, 10, 6, 30, 2, 14, 10, 70, 6, 42, 30, 210, 2, 22, 14, 154, 10, 110, 70, 770, 6, 66, 42, 462, 30, 330, 210, 2310, 2, 26, 22, 286, 14, 182, 154, 2002, 10, 130, 110, 1430, 70, 910, 770, 10010, 6, 78, 66, 858, 42, 546, 462, 6006, 30, 390, 330, 4290, 210, 2730
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| All terms have 2-valuation equal to 1, i.e. they equal twice an odd (and square-free) number, since the first digit in base two will always be "1". - M. F. Hasler, Mar 25 2011.
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EXAMPLE
| a(7) = 2*3*5 = 30. binary 7 = 111,
a(10) = 2^1*3^0*5^1*7^0 =10, binary(10) = 1010.
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PROG
| (PARI) a(n)=factorback(Mat(vector(#n=binary(n), j, [prime(j), n[j]])~))
(PARI) a(n)=prod(j=1, #n=binary(n), prime(j)^n[j]) \\ - M. F. Hasler, Mar 25 2011
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CROSSREFS
| Cf. A110766.
Sequence in context: A096869 A154009 A099985 * A176991 A091818 A071223
Adjacent sequences: A110762 A110763 A110764 * A110766 A110767 A110768
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KEYWORD
| base,easy,nonn
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Aug 12 2005
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EXTENSIONS
| More terms from Stacy Hawthorne (shawtho1(AT)ashland.edu), Oct 31 2005
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