Numbers n such that n, sigma(n) and sigma(sigma(n)) are odd.

A231484

Numbers n such that n, sigma(n) and sigma(sigma(n)) are odd.

Terms

    a(0) =1a(1) =81a(2) =1476326929a(3) =10994571025a(4) =61436066769a(5) =98551417041a(6) =119582481249a(7) =141447449025a(8) =220545762129a(9) =388895668225a(10) =619568914129a(11) =890560253025a(12) =970952066161

External references