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A135833
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Number of Section I primes between 2^n and 2^(n+1). See A135832.
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2
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1, 2, 2, 4, 5, 7, 9, 13, 18, 21, 28, 43, 56, 62, 72, 94, 133, 142, 187, 241, 313, 376, 436, 517, 709, 858, 982, 1271, 1561, 1814, 2192, 2658, 3184, 3853, 4601, 5648, 6881, 8009, 9535, 11651, 13712, 16325, 19381, 23323, 27097, 31782, 37924, 44673, 52695, 62147
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Comparing these numbers with A036378, the number of primes between 2^n and 2^(n+1), leads one to conjecture that the density of Section I primes is 0.
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LINKS
| T. D. Noe, Computing Numbers in Section I of the Totient Iteration [From T. D. Noe (noe(AT)sspectra.com), Nov 18 2008]
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EXAMPLE
| 3; 5, 7; 11, 13; 17, 23, 29, 31; 41, 47, 53, 59, 61; 83,...
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MATHEMATICA
| class[ n_ ] := Length[ NestWhileList[ EulerPhi, n, #>2& ] ]-1; k=2; Table[ cnt=0; While[ p=Prime[ k ]; p<2^(n+1), If[ class[ p ]==n, cnt++ ]; k++ ]; cnt, {n, 20} ] [ From T. D. Noe (noe(AT)sspectra.com), Aug 04 2008 ]
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CROSSREFS
| Cf. A092878 (number of odd numbers in Section I).
Sequence in context: A000726 A128663 A174068 * A137200 A026930 A098859
Adjacent sequences: A135830 A135831 A135832 * A135834 A135835 A135836
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KEYWORD
| nonn
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AUTHOR
| T. D. Noe (noe(AT)sspectra.com), Nov 30 2007
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EXTENSIONS
| More terms from T. D. Noe (noe(AT)sspectra.com), Aug 04 2008
Extension. T. D. Noe (noe(AT)sspectra.com), Nov 18 2008
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