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#23 by N. J. A. Sloane at Sun Mar 04 13:39:24 EST 2018
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#22 by Chai Wah Wu at Sun Mar 04 13:10:47 EST 2018
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#21 by Chai Wah Wu at Sun Mar 04 13:10:37 EST 2018
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| EXTENSIONS
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DefinitionComment clarified by Chai Wah Wu, Mar 04 2018
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| STATUS
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proposed
editing
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#20 by Chai Wah Wu at Sun Mar 04 13:02:14 EST 2018
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Discussion
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| Sun Mar 04
| 13:05
| Michel Marcus: you did not change the name but a comment, so rather sign comment ?
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#19 by Chai Wah Wu at Sun Mar 04 13:02:02 EST 2018
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| FORMULA
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From Chai Wah Wu, Mar 04 2018: (Start)
a(n) = 2*a(n-30) - a(n-60) for n > 60.
G.f.: x*(6*x^58 + x^57 + x^56 + 2*x^55 + x^54 + 3*x^53 + 48*x^52 + 4*x^51 + 3*x^50 + 5*x^49 + 76*x^48 + 6*x^47 + 90*x^46 + 7*x^45 + 5*x^44 + 8*x^43 + 118*x^42 + 9*x^41 + 132*x^40 + 10*x^39 + 7*x^38 + 11*x^37 + 160*x^36 + 12*x^35 + 5*x^34 + 13*x^33 + 9*x^32 + 14*x^31 + 202*x^30 + 15*x^29 + 204*x^28 + 14*x^27 + 9*x^26 + 13*x^25 + 5*x^24 + 12*x^23 + 162*x^22 + 11*x^21 + 7*x^20 + 10*x^19 + 134*x^18 + 9*x^17 + 120*x^16 + 8*x^15 + 5*x^14 + 7*x^13 + 92*x^12 + 6*x^11 + 78*x^10 + 5*x^9 + 3*x^8 + 4*x^7 + 50*x^6 + 3*x^5 + x^4 + 2*x^3 + x^2 + x + 8)/(x^60 - 2*x^30 + 1). (End)
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#18 by Chai Wah Wu at Sun Mar 04 12:49:29 EST 2018
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| PROG
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return n//2 if not n % 2 else (n//3 if not n % 3 else (n//5 if not n % 5 else 7*n+1)) # Chai Wah Wu, Mar 04 2018
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#17 by Chai Wah Wu at Sun Mar 04 12:49:19 EST 2018
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| PROG
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(Python)
from __future__ import division
def A133421(n):
return n//2 if not n % 2 else (n//3 if not n % 3 else (n//5 if not n % 5 else 7*n+1)) # Chai Wah Wu, Mar 04 2018
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#16 by Chai Wah Wu at Sun Mar 04 12:43:46 EST 2018
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| COMMENTS
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The 7x+1 map sends x to x/2 if x is even, x/3 if x is odd and divisible by 3, x/5 if x is not divisible by 6 and divisible by 5, otherwise 7x+1.
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| EXTENSIONS
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Definition clarified by Chai Wah Wu, Mar 04 2018
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| STATUS
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approved
editing
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#15 by Charles R Greathouse IV at Wed Sep 02 14:40:37 EDT 2015
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#14 by Charles R Greathouse IV at Wed Sep 02 14:40:35 EDT 2015
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