A072416 -id:A072416 - cp's OEIS frontend

A072415 a(1) = 2; a(n) = a(n-1)-th even nontotient number.

2, 26, 182, 878, 3626, 13508, 46922, 155156, 494468, 1529590, 4615074, 13633310, 39548078, 112918434, 317920082, 883996002

Offset: 1

Labos Elemer, Jun 17 2002

Cf. A006508, A071255, A005277, A072416.

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, 8}]

a(3)=182 is the 26th = a(2)-th term in A005277.

Edited by Robert G. Wilson v, Jun 20 2002

a(11)-a(16) from Donovan Johnson, Oct 29 2010

A071598 a(0) = 1; a(n) = half of the a(n-1)-th even nontotient number.

Original entry on oeis.org

1, 7, 34, 115, 298, 677, 1431, 2853, 5401, 9813, 17289, 29687, 49901, 82315, 133617, 213801, 337742, 527231, 814218, 1244962, 1886069, 2833392, 4223121, 6247850, 9179762, 13399951, 19440903, 28043882, 40233399, 57423953, 81557903

Offset: 0

Robert G. Wilson v, Jun 20 2002

nonn

			a(5) = 677 = 1354/2, where 1354 is the a(4) = 298th term in A005277. [Corrected by _Sean A. Irvine_, Jul 28 2024]

Cf. A005277, A072416.

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 = b[[c]], {n, 0, 18}]

a(19)-a(30) from Donovan Johnson, May 30 2010

cp's OEIS Frontend

A072415 a(1) = 2; a(n) = a(n-1)-th even nontotient number.

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