A038487 Sums of two distinct powers of 9.

10, 82, 90, 730, 738, 810, 6562, 6570, 6642, 7290, 59050, 59058, 59130, 59778, 65610, 531442, 531450, 531522, 532170, 538002, 590490, 4782970, 4782978, 4783050, 4783698, 4789530, 4842018, 5314410, 43046722, 43046730, 43046802, 43047450, 43053282

Offset: 1

Author

Olivier Gérard

Keywords

• nonn
• easy

Links

• Robert Israel, Table of n, a(n) for n = 1..10001

Crossrefs

Base 9 interpretation of A038444.

Programs

Maple

N:= 10^10: # to get all terms <= N
{seq(seq(9^a+9^b,b=0..a-1),a=1..floor(log[9](N)))}; # Robert Israel, Aug 31 2014

Mathematica

Total/@Subsets[9^Range[0,10],{2}]//Union (* Harvey P. Dale, Aug 25 2023 *)

PARI

for(a=0,19,for(b=0,a-1,print1(9^a+9^b,","))) \\ M. F. Hasler, Aug 31 2014

Python

from math import isqrt
def A038487(n): return 9**(m:=isqrt(n<<3)+1>>1)+9**(n-1-(m*(m-1)>>1)) # Chai Wah Wu, Apr 05 2025

Formula

a(n)=9^A002024(n)+9^A002262(n). - M. F. Hasler, Aug 31 2014

Extensions

More terms from Vincenzo Librandi, Aug 06 2009

Corrected by Harvey P. Dale, Aug 31 2014

Offset changed from 0 to 1 by M. F. Hasler, Aug 31 2014