A072415 -id:A072415 - cp's OEIS frontend

A072416 a(1) = 2; a(n) = half of the a(n-1)-th even nontotient number.

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

Offset: 1

Labos Elemer, Jun 17 2002

nonn

Cf. A006508, A071255, A005277, A072415.

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}]

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

Edited by Robert G. Wilson v, Jun 20 2002

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

A071573 a(1) = 1; a(n) = a(n-1)-th nontotient number.

Original entry on oeis.org

1, 14, 114, 594, 2532, 9658, 34066, 113930, 366358, 1141614, 3465398, 10291022, 29988178, 85961454, 242870564, 677436550, 1867877934

Offset: 1

Robert G. Wilson v, Jun 20 2002

Cf. A005277, A072415.

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 = 1; Do[ Print[c]; c = 2b[[c]], {n, 0, 7}]

a(3)=114 is the 14th = a(2)-th term in A005277.

Changed offset to match formula and a(11)-a(17) from Donovan Johnson, Feb 12 2011

cp's OEIS Frontend

A072416 a(1) = 2; a(n) = half of the a(n-1)-th even nontotient number.

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