A063480 C(n+3)=2*C(n), where C(n) is Cototient(n) := n - phi(n) (A051953).

39, 55, 111, 183, 219, 459, 471, 579, 831, 867, 939, 1191, 1263, 1371, 1623, 1839, 1983, 2019, 2199, 2271, 2631, 2991, 3279, 3459, 3603, 3639, 3711, 3963, 4143, 4359, 4863, 4947, 4971, 5259, 5619, 5799, 5979, 6051, 6411, 7023, 7107, 7419, 7671, 7779

Offset

1,1

Links

Harry J. Smith, Table of n, a(n) for n=1,...,1000

Example

C(39) = 15, C(39+3) = 2*15.

Prog

(PARI) C(n)=n-eulerphi(n); j=[]; for(n=1, 20000, if(C(n+3)==2*C(n), j=concat(j, n))); j
(PARI) { n=0; c1=c2=c3=1; for (m=1, 10^9, c=c1; c1=c2; c2=c3; c3=m-eulerphi(m); if (c3==2*c, write("b063480.txt", n++, " ", m - 3); if (n==1000, break)) ) } \\ Harry J. Smith, Aug 23 2009

Crossrefs

Cf. A059153.

Sequence in context: A319983 A165346 A268083 * A305026 A009633 A327586

Adjacent sequences: A063477 A063478 A063479 * A063481 A063482 A063483

Keyword

nonn

Author

Jason Earls, Jul 28 2001

Status

approved