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A072416 a(1) = 2; a(n) = half of the a(n-1)-th even nontotient number. 2
2, 13, 49, 149, 373, 835, 1727, 3383, 6341, 11419, 19966, 34067, 56967, 93578, 151313, 241281, 379934, 591413, 910879, 1389289, 2099905, 3147743, 4682362, 6914234, 10141072, 14779023, 21408820, 30837491, 44179913, 62974570, 89329823 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..31.

FORMULA

a(5) = 373 = 746/2, where 746 is the a(4) = 149th term in A005277.

MATHEMATICA

a = Table[0, {10^6}]; Do[b = EulerPhi[n]/2; If[b < 10^6 + 1, a[[b]] = 1], {n, 1, 2 10^7}]; b = Select[ Range[10^6], a[[ # ]] == 0 &]; c = 2; Do[ Print[c]; c = b[[c]], {n, 0, 17}]

CROSSREFS

Cf. A006508, A071255, A005277, A072415.

Sequence in context: A270294 A330539 A005584 * A319759 A254784 A056305

Adjacent sequences:  A072413 A072414 A072415 * A072417 A072418 A072419

KEYWORD

nonn

AUTHOR

Labos Elemer, Jun 17 2002

EXTENSIONS

Edited by Robert G. Wilson v, Jun 20 2002

a(18)-a(31) from Donovan Johnson, Oct 29 2010

STATUS

approved

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Last modified May 12 10:10 EDT 2021. Contains 343821 sequences. (Running on oeis4.)