A053162 Nonprimes n such that n+cototient(n) is a power of 2.
1, 10, 20, 40, 80, 160, 320, 322, 640, 644, 1280, 1288, 2560, 2576, 5120, 5152, 10240, 10304, 20480, 20608, 40960, 41216, 81920, 82432, 163840, 164864, 327680, 329728, 333634, 655360, 659456, 667268, 1310720, 1318912, 1334536, 1378114, 2621440
Offset: 1
Keywords
Examples
Mersenne primes were deleted from set of numbers with similar property. An infinite subset here is m(r)=5*2^r, since Phi[m(r)]=2^(r+1) and a(m(r))=5*2^(r+1)-2^(r+1)=2^(r+3). A different subset includes m = 322,644,1288,.. = Set of {(2^s)*7*23} generating 2^(s+8)=2m-Phi(m) powers of 2.
Links
- Donovan Johnson, Table of n, a(n) for n = 1..100
Programs
-
PARI
for(n=1, 2621440, if(isprime(n)==0, if(omega((2*n-eulerphi(n))*2)==1, print1(n ", ")))) \\ Donovan Johnson, Jan 09 2014
Extensions
More terms from Olaf Voß, Feb 25 2008
Comments