Numbers of the form x = 2^k*p*q, p,q odd primes, such that sigma(x)/phi(x) = 4.

Terms

a(0) =418a(1) =3596a(2) =3956a(3) =5396a(4) =8636a(5) =41656a(6) =56536a(7) =393104a(8) =2072608a(9) =2316448a(10) =6543008a(11) =17434528a(12) =135394432a(13) =217023616a(14) =1264918784a(15) =1490909824a(16) =2710540544a(17) =11444858368a(18) =17669583104a(19) =34797058304a(20) =37698861568a(21) =70572901376a(22) =132968907776a(23) =226965472256a(24) =233356030976a(25) =552070776832a(26) =596357220352a(27) =601188468736