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

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

0,2

Links

Table of n, a(n) for n=0..30.

Example

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

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 = 1; Do[ Print[c]; c = b[[c]], {n, 0, 18}]

Crossrefs

Cf. A005277, A072416.

Sequence in context: A195018 A024817 A201230 * A224036 A120470 A377883

Adjacent sequences: A071595 A071596 A071597 * A071599 A071600 A071601

Keyword

nonn

Author

Robert G. Wilson v, Jun 20 2002

Extensions

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

Status

approved