A062958 Numbers k such that phi(k+1) < 2*phi(k), where phi = A000010.

1, 3, 5, 7, 8, 9, 11, 13, 14, 15, 17, 19, 20, 21, 23, 25, 26, 27, 29, 31, 32, 33, 34, 35, 37, 38, 39, 41, 43, 44, 45, 47, 49, 50, 51, 53, 55, 56, 57, 59, 61, 62, 63, 64, 65, 67, 68, 69, 71, 73, 74, 75, 76, 77, 79, 80, 81, 83, 85, 86, 87, 89, 91, 92, 93, 94, 95, 97, 98, 99, 101

Offset

1,2

Links

Table of n, a(n) for n=1..71.

Mathematica

Flatten[Position[Partition[EulerPhi[Range[110]], 2, 1], _?(#[[2]]< 2*#[[1]]&)]]//Quiet(* Harvey P. Dale, Apr 04 2015 *)

Prog

(PARI) j=[]; for(n=1, 200, if(eulerphi(n+1)<2*eulerphi(n), j=concat(j, n))); j

Crossrefs

Cf. A000010.

Sequence in context: A072668 A249433 A300737 * A295075 A184996 A153309

Adjacent sequences: A062955 A062956 A062957 * A062959 A062960 A062961

Keyword

nonn

Author

Jason Earls, Jul 26 2001

Status

approved