A038488 Sums of 3 distinct powers of 9.
91, 739, 811, 819, 6571, 6643, 6651, 7291, 7299, 7371, 59059, 59131, 59139, 59779, 59787, 59859, 65611, 65619, 65691, 66339, 531451, 531523, 531531, 532171, 532179, 532251, 538003, 538011, 538083, 538731, 590491, 590499, 590571, 591219, 597051, 4782979, 4783051
Offset: 1
Links
- Amiram Eldar, Table of n, a(n) for n = 1..10000
Programs
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Mathematica
Sort[Plus @@@ Subsets[9^Range[0, 6], {3}]] (* Amiram Eldar, Jul 14 2022 *) -
Python
from math import isqrt, comb from sympy import integer_nthroot def A038488(n): return 9**((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))+9**((a:=isqrt(s:=n-comb(m-(t^1)+2,3)<<1))+((s<<2)>(a<<2)*(a+1)+1))+9**(m+t+1) # Chai Wah Wu, Apr 05 2025
Extensions
Offset corrected by Amiram Eldar, Jul 14 2022