A038478 Sums of 2 distinct powers of 6.

7, 37, 42, 217, 222, 252, 1297, 1302, 1332, 1512, 7777, 7782, 7812, 7992, 9072, 46657, 46662, 46692, 46872, 47952, 54432, 279937, 279942, 279972, 280152, 281232, 287712, 326592, 1679617, 1679622, 1679652, 1679832, 1680912, 1687392, 1726272, 1959552, 10077697, 10077702

Offset: 1

Author

Olivier Gérard

Keywords

• nonn
• easy

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Base-6 interpretation of A038444.

Cf. A000400, A038479, A038480.

Programs

Mathematica

Total/@Subsets[6^Range[0,10],{2}]//Union (* Harvey P. Dale, Aug 11 2018 *)

Python

from math import isqrt
def A038478(n): return 6**(m:=isqrt(n<<3)+1>>1)+6**(n-1-(m*(m-1)>>1)) # Chai Wah Wu, Apr 04 2025

Extensions

Offset corrected by Amiram Eldar, Jul 14 2022