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A055257
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Sums of two powers of 6.
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0
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2, 7, 12, 37, 42, 72, 217, 222, 252, 432, 1297, 1302, 1332, 1512, 2592, 7777, 7782, 7812, 7992, 9072, 15552, 46657, 46662, 46692, 46872, 47952, 54432, 93312, 279937, 279942, 279972, 280152, 281232, 287712, 326592, 559872, 1679617, 1679622, 1679652, 1679832
(list; table; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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FORMULA
| a(n) = 6^(n-trinv(n))+6^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)=6^n+6^k, so as a sequence a(n) =6^A002262(n)+6^A003056(n).
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EXAMPLE
| a(4) = 42 = 6^2+6^1
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MATHEMATICA
| t = 6^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: A088662 A073710 A092831 * A084068 A192772 A046243
Adjacent sequences: A055254 A055255 A055256 * A055258 A055259 A055260
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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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