A350277 Indices of records in A349325.

1, 3, 6, 7, 14, 19, 54, 73, 129, 313, 353, 470, 5838, 10855, 14473, 26283, 60220, 60221, 155897, 445089, 1098406, 1168014, 1169865, 4143030, 8546945, 10964814, 11395926, 31273927, 590633697, 1117772702, 1240568869, 1240568870, 2845683047, 2963752572, 2963752573

Offset

1,2

Links

Chai Wah Wu, Table of n, a(n) for n = 1..39

Index entries for sequences related to 3x+1 (or Collatz) problem

Mathematica

A349325[n_]:=Module[{h=1, c=n, prevc=n}, While[c>1, If[OddQ[c], c=(3c+1)/2; If[prevc<n&&c>n, h++], c/=2^IntegerExponent[c, 2]; If[prevc>n&&c<n, h++]]; prevc=c]; h]
upto=10000; a={}; rec=-1; Do[If[(r=A349325[i])>rec, rec=r; AppendTo[a, i]], {i, upto}]; a

Prog

(Python)
def A349325(n):
    prevc = c = n
    h = 1
    while c > 1:
        if c % 2:
            c = (3*c+1) // 2
            if prevc < n and c > n: h += 1
        else:
            c //= 2
            if prevc > n and c < n: h += 1
        prevc = c
    return h
rec, rec_idx = -1, []
for i in range(1, 10000):
    r = A349325(i)
    if r > rec:
        rec = r
        rec_idx.append(i)
print(rec_idx)

Crossrefs

Cf. A349325, A350278.

Sequence in context: A056055 A359476 A070523 * A350278 A233757 A341622

Adjacent sequences: A350274 A350275 A350276 * A350278 A350279 A350280

Keyword

nonn,hard

Author

Paolo Xausa, Dec 22 2021

Extensions

a(24)-a(35) from Chai Wah Wu, Jan 04 2022

Status

approved