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.

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

Crossrefs

Cf. A005277, A072416.

Sequence in context: A195018 A024817 A201230 * A224036 A120470 A036423

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