A337066 a(n) is the smallest k such that A336957(k) = n, or -1 if n does not appear in A336957.

1, 2, -1, -1, -1, 3, -1, -1, -1, 10, -1, 7, -1, 6, 4, -1, -1, 11, -1, 15, 12, 14, -1, 35, -1, 18, -1, 19, -1, 31, -1, -1, 8, 22, 5, 39, -1, 23, 17, 27, -1, 30, -1, 43, 16, 26, -1, 67, -1, 42, 21, 47, -1, 71, 9, 34, 24, 51, -1, 63, -1, 46, 20, -1, 28, 75, -1, 55, 25, 50, -1, 79, -1, 54, 36, 38

Offset: 1

Author

Scott R. Shannon and N. J. A. Sloane, Aug 13 2020

Keywords

• sign

Comments

There is a strong conjecture that numbers n >= 3 appear in A336957 if and only if they are divisible by at least two different primes.

Links

• Scott R. Shannon, Table of n, a(n) for n = 1..20000

Crossrefs

Cf. A098550, A336957, A337007, A337008.