A342815 Numbers of the form (2^(2*j + 6*k + 5) - 2^(2*j + 1) - 3)/9, with j,k >= 0.

3, 13, 53, 213, 227, 853, 909, 3413, 3637, 13653, 14549, 14563, 54613, 58197, 58253, 218453, 232789, 233013, 873813, 931157, 932053, 932067, 3495253, 3724629, 3728213, 3728269, 13981013, 14898517, 14912853, 14913077, 55924053, 59594069, 59651413, 59652309

Offset

1,1

Comments

Sequence is a subsequence of A198584. When any term is iterated using the Collatz function, the last odd integer in the trajectory before 1 is of the form (4^(3*m + 2) - 1)/3.

Links

Table of n, a(n) for n=1..34.

Satya Das, Extension of speeded up Collatz map to the real line

Mathematica

Take[Sort[Flatten[Table[(2^(2n1+6n2+5) - 2^(2n1+1) - 3)/9, {n1, 0, 20}, {n2, 0, 20}]]], 50]

Prog

(Python)
seq=[]
for n1 in range(20):
    for n2 in range(20):
        n=(2**(2*n1+6*n2+5) - 2**(2*n1+1) - 3)/9
        seq.append(n)
seq.sort()
print(seq[0:50])

Crossrefs

Union with A342816 gives A198584.

Sequence in context: A065059 A198584 A346382 * A072197 A065838 A052990

Adjacent sequences: A342812 A342813 A342814 * A342816 A342817 A342818

Keyword

nonn,easy

Author

Satya Das, Mar 22 2021

Status

approved