Irregular triangle, read by rows, where row n lists composite numbers c such that c * sigma_n(c) == 2 (mod phi(c)) for n >= 0. Row lengths for n=0,1,... are given in A392307.
A392306
Irregular triangle, read by rows, where row n lists composite numbers c such that c * sigma_n(c) == 2 (mod phi(c)) for n >= 0. Row lengths for n=0,1,... are given in A392307.
Terms
- a(0) =4a(1) =6a(2) =14a(3) =4a(4) =6a(5) =22a(6) =4a(7) =6a(8) =14a(9) =38a(10) =4a(11) =6a(12) =4a(13) =6a(14) =14a(15) =46a(16) =134a(17) =4a(18) =6a(19) =22a(20) =262a(21) =4a(22) =6a(23) =14a(24) =4a(25) =6a(26) =4a(27) =6a(28) =14a(29) =38
External references
- oeis: A392306