A368383 a(n) = index of n in A368382, or -1 if n is missing from that sequence.

1, 7, 2, 5, 13, 3, 67, 35, 11, 33, 4, 31, 6, 29, 8, 27, 63, 25, 327, 23, 61, 21, 325, 19, 59, 17, 323, 15, 57, 9, 321, 175, 55, 173, 15490, 171, 53, 169, 317, 167, 51, 165, 1167, 163, 49, 161, 10, 159, 47, 157, 12, 155, 45, 153, 14, 151, 16, 149, 18, 147, 20, 145, 22, 143, 24, 141, 26, 139, 28, 137, 30, 135, 32, 133, 34

Offset

1,2

Links

Chai Wah Wu, Table of n, a(n) for n = 1..10000

Prog

(Python)
from itertools import count
def A368383(n):
    a, aset, p = 1, {0, 1}, 2
    for c in count(1):
        if a==n: return c
        for b in count(a%p, p):
            if b not in aset:
                aset.add(b)
                a, p = b, 3 if p == 2 else p+2
                break # Chai Wah Wu, Mar 05 2024
(Python) # faster for initial segment of sequence
def A368383_gen(): # uses A368382_gen/imports from Chai Wah Wu in A368382
    adict, n = dict(), 1
    for i, v in enumerate(A368382_gen(), 1):
        if v >= n and v not in adict:
            adict[v] = i
            while n in adict:
                yield adict[n]; del adict[n]; n += 1
print(list(islice(A368383_gen(), 63))) # Michael S. Branicky, Apr 18 2024

Crossrefs

Sequence in context: A006577 A337150 A280234 * A073652 A277848 A248285

Adjacent sequences: A368380 A368381 A368382 * A368384 A368385 A368386

Keyword

nonn,changed

Author

N. J. A. Sloane, Mar 03 2024

Status

approved