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A055260
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Sums of two powers of 9.
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0
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2, 10, 18, 82, 90, 162, 730, 738, 810, 1458, 6562, 6570, 6642, 7290, 13122, 59050, 59058, 59130, 59778, 65610, 118098, 531442, 531450, 531522, 532170, 538002, 590490, 1062882, 4782970, 4782978, 4783050, 4783698, 4789530, 4842018, 5314410, 9565938, 43046722
(list; table; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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FORMULA
| a(n) = 9^(n-trinv(n))+9^trinv(n), where trinv(n) = floor((1+sqrt(1+8*n))/2) = A002262(n) and n-trinv(n) = A003056(n)
Regarded as a triangle T(n, k)=9^n+9^k, so as a sequence a(n) =9^A002262(n)+9^A003056(n).
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EXAMPLE
| a(4) = 90 = 9^2+9^1
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MATHEMATICA
| t = 9^Range[0, 9]; Select[Union[Flatten[Table[i + j, {i, t}, {j, t}]]], # <= t[[-1]] + 1 &] (* T. D. Noe, Oct 09 2011 *)
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CROSSREFS
| Cf. A052216.
Sequence in context: A018227 A092062 A134251 * A180591 A156446 A032685
Adjacent sequences: A055257 A055258 A055259 * A055261 A055262 A055263
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KEYWORD
| easy,nonn,tabl
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AUTHOR
| Henry Bottomley (se16(AT)btinternet.com), Jun 22 2000
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