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A072297
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Number of even non-cototients not exceeding 2^n.
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0
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0, 0, 0, 1, 2, 6, 10, 23, 48, 99, 194, 392, 791, 1600, 3290, 6810, 13900, 28269, 57455, 116213, 234237, 470861, 945510, 1897007, 3802257, 7616206, 15244011, 30493702, 60965480, 121838430, 243409121, 486131077
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,5
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EXAMPLE
| a(6)=6 because the even non-cototients not exceeding 64 are {10,26,34,50,52&58}.
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MATHEMATICA
| a = Table[0, {2^26}]; Do[ b = n - EulerPhi[n]; If[ EvenQ[b] && b < 2^27 + 1, a[[b/2]]++ ], {n, 2, 10^9}]; c = 0; k = 1; Do[While[k < 2^n, If[a[[k]] == 0, c++ ]; k++ ]; Print[c], {n, 1, 26}]
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CROSSREFS
| Number of terms in A063740 <= 2^n. Cf. A072077.
Sequence in context: A200572 A049750 A134016 * A183036 A120963 A200220
Adjacent sequences: A072294 A072295 A072296 * A072298 A072299 A072300
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KEYWORD
| hard,nonn
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Jul 13 2002 and Jul 29 2002
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EXTENSIONS
| a(16) and a(21) corrected and a(28)-a(32) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Jun 23 2010
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