A193293 -id:A193293 - cp's OEIS frontend

A255686 Numbers n such that lambda(sum of odd divisors of Fibonacci(n)) = lambda(sum of even divisors of Fibonacci(n)) where lambda is the Carmichael function (A002322).

3, 9, 12, 15, 18, 21, 27, 33, 39, 45, 51, 63, 69, 87, 93, 111, 123, 135, 141, 153, 159, 177, 189, 201, 219, 225, 237, 249, 255, 267, 291, 303, 309, 321, 339, 363, 381, 393, 411, 423, 453, 459, 501, 537, 543, 573, 579, 633, 669, 699

Offset: 1

Michel Lagneau, Mar 02 2015

nonn

Number n such that A002322(A193293(n))= A002322(A193294(n)).

a(n) is divisible by 3, and a majority of numbers a(n)/3 are primes: 3, 5, 7, 11, 13, 17, 23, 29, 31, 37, 41, 47, 53, 59, 67, 73, 79, 83, 89, 97, 101, 103, 107, 113, 127, 131, 137, 151, 167, 179, 181, 191, 193, 211, 223, 233, ... The nonprimes a(n)/3 are 1, 4, 6, 9, 15, 21, 45, 51, 63, 75, 121, 153, ...

			18 is in the sequence because A002322(A193293(18)) = A002322(360) = 12 and A002322(A193294(18))= A002322(5040) = 12.

Cf. A000045, A002322, A193293, A193294.

f[x_] := Plus @@ Select[Divisors[Fibonacci[x]], OddQ[#] &]; g[x_] := Plus @@ Select[Divisors[Fibonacci[x]], EvenQ[#]&];Do[If[CarmichaelLambda[f[n]]== CarmichaelLambda[g[n]],Print[n]],{n,1,500}]

a002322(n) = lcm(znstar(n)[2]);
isok(n) = my(fn = fibonacci(n)); my(sod = sumdiv(fn, d, d*(d%2))); my(sed = sigma(fn) - sod); sod && sed && (a002322(sod) == a002322(sed)); \\ Michel Marcus, Mar 02 2015

cp's OEIS Frontend

A255686 Numbers n such that lambda(sum of odd divisors of Fibonacci(n)) = lambda(sum of even divisors of Fibonacci(n)) where lambda is the Carmichael function (A002322).

Views

Author

Keywords

Comments

Examples

Crossrefs

Programs

Mathematica

PARI