A343926 a(n) is the least k such that A343443(k) = n or 0 if there is no such k.

1, 0, 2, 4, 8, 16, 32, 64, 6, 256, 512, 12, 2048, 4096, 24, 36, 32768, 48, 131072, 72, 96, 1048576, 2097152, 144, 216, 16777216, 30, 288, 134217728, 432, 536870912, 576, 1536, 4294967296, 864, 60, 34359738368, 68719476736, 6144, 1728, 549755813888, 2592, 2199023255552

Offset

1,3

Comments

The indices for which a(n) = 2^(n-2) appear to be A232803. - Michel Marcus, May 05 2021

This is true. We can check it for n <= 10. For n > 10 there are only primes and twice primes in A232803. Any number k > 10 not in A232803 can be factored as k = m*p where m, p > 2 and m >= p. We then have A343443(2^(m-2)*3^(p-2)) = m*p = k. But 2^(k-2) = 2^(m*p-2) > 2^(m-2)*3^(p-2). As m, p > 2 we have 2^(m-2)*3^(p-2) not in A232803. - David A. Corneth, May 05 2021

Links

David A. Corneth, Table of n, a(n) for n = 1..3325 (first 52 terms from Michel Marcus)

Formula

a(n) <= 2^(n-2) for n >= 3.

Crossrefs

Cf. A025487, A232803, A343443.

Sequence in context: A025489 A160686 A201920 * A223700 A036140 A036138

Adjacent sequences: A343923 A343924 A343925 * A343927 A343928 A343929

Keyword

nonn

Author

Michel Marcus, May 04 2021

Status

approved