A118129 Numbers k such that the sum of the first k odd composites is palindromic in base 3.

6, 14, 20, 424, 1042, 8290, 20802, 21644, 440512, 548008, 749171, 4366390, 5378548, 9850174, 17930596, 36158854, 130427194, 407305710, 3077094752, 93416875260

Offset

1,1

Comments

No more terms through 10^9.

Any subsequent terms are > 10^11. - Lucas A. Brown, Aug 12 2024

Links

Table of n, a(n) for n=1..20.

Lucas A. Brown, Python program.

Example

The sum of the first 14 odd composites, when written in base 3, is the palindrome 201102, so 14 is in the sequence.

Crossrefs

Cf. A058848 (palindromic in base 10).

Sequence in context: A064709 A371396 A397411 * A046712 A162823 A020171

Adjacent sequences: A118126 A118127 A118128 * A118130 A118131 A118132

Keyword

nonn,base,hard,more

Author

Ryan Propper, May 12 2006

Extensions

a(19)-a(20) from Lucas A. Brown, Aug 12 2024

Status

approved