Numbers n such that phi(2n-1) = sigma(n).

Terms

a(0) =1a(1) =3a(2) =5a(3) =10a(4) =11a(5) =23a(6) =33a(7) =46a(8) =65a(9) =77a(10) =123a(11) =136a(12) =221a(13) =371a(14) =383a(15) =423a(16) =483a(17) =513a(18) =545a(19) =670a(20) =753a(21) =1643a(22) =2033a(23) =3838a(24) =3885a(25) =4533a(26) =4798a(27) =5177a(28) =7463a(29) =7739