A038485 Sums of 3 distinct powers of 8.

73, 521, 577, 584, 4105, 4161, 4168, 4609, 4616, 4672, 32777, 32833, 32840, 33281, 33288, 33344, 36865, 36872, 36928, 37376, 262153, 262209, 262216, 262657, 262664, 262720, 266241, 266248, 266304, 266752, 294913, 294920, 294976, 295424, 299008, 2097161, 2097217

Offset: 1

Author

Olivier Gérard

Keywords

• nonn
• easy

Links

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

Crossrefs

Base-8 interpretation of A038445.

Cf. A001018, A038484, A038486.

Programs

Mathematica

Take[Union[Total/@Subsets[8^Range[0,10],{3}]],40] (* Harvey P. Dale, Jan 31 2016 *)

Python

from math import isqrt, comb
from sympy import integer_nthroot
def A038485(n): return (1<<3*((r:=n-1-comb((m:=integer_nthroot(6*n,3)[0])+(t:=(n>comb(m+2,3)))+1,3))-comb((k:=isqrt(b:=r+1<<1))+(b>k*(k+1)),2)))+(1<<3*((a:=isqrt(s:=n-comb(m-(t^1)+2,3)<<1))+((s<<2)>(a<<2)*(a+1)+1)))+(1<<3*(m+t+1)) # Chai Wah Wu, Apr 05 2025

Extensions

Offset corrected by Amiram Eldar, Jul 14 2022