A392755 a(n) = the largest value of k such that A381466(k) = n or -1 if no such k exists.

-1, 8, 48, 0, 75, 24, 56, 32, 144, 20, 99, -1, 52, -1, 135, 13, -1, 72, 570, 40, 315, 44, 207, 192, 675, -1, 243, -1, 174, -1, 279, 64, -1, 68, -1, 31, 1110, -1, 390, 80, 246, 168, 387, 176, 90, -1, 423, 96, -1, -1, 459, 104, 795, 108, 1650, -1, 912, 39, 531, 120, 1037, 19, 567

Offset

1,2

Comments

A particular value k must appear in A381466 at or before index 6*k^2 - 2*k. If such a k doesn't appear in A381466 by then, a(k) = -1.

Links

Sam Chapman, Table of n, a(n) for n = 1..2000

Example

a(1) = a(12) = -1 since 1 and 12 never appear in A381466.
a(2) = 8 since A381466(8) = 2 is the last time that 2 appears in that sequence.

Crossrefs

Cf. A381466, A133058, A091508.

Sequence in context: A034349 A296797 A024108 * A247726 A385165 A263506

Adjacent sequences: A392752 A392753 A392754 * A392756 A392757 A392758

Keyword

sign

Author

Sam Chapman, Jan 21 2026

Status

approved