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A055237 Sums of two powers of 5. 2
2, 6, 10, 26, 30, 50, 126, 130, 150, 250, 626, 630, 650, 750, 1250, 3126, 3130, 3150, 3250, 3750, 6250, 15626, 15630, 15650, 15750, 16250, 18750, 31250, 78126, 78130, 78150, 78250, 78750, 81250, 93750, 156250, 390626, 390630, 390650, 390750, 391250, 393750 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

T. D. Noe, Rows n = 0..100 of triangle, flattened

FORMULA

a(n) = 5^(n-trinv(n))+5^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) = 5^n + 5^k, so as a sequence a(n) = 5^A002262(n) + 5^A003056(n).

MATHEMATICA

t = 5^Range[0, 9]; Select[Union[Flatten[Table[i + j, {i, t}, {j, t}]]], # <= t[[-1]] + 1 &] (* T. D. Noe, Oct 09 2011 *)

Total/@Tuples[5^Range[0, 9], 2]//Union (* Harvey P. Dale, Jan 29 2017 *)

CROSSREFS

Cf. A052216.

Sequence in context: A104142 A258143 A079713 * A057434 A217381 A162581

Adjacent sequences:  A055234 A055235 A055236 * A055238 A055239 A055240

KEYWORD

easy,nonn,tabl

AUTHOR

Henry Bottomley, Jun 22 2000

STATUS

approved

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Last modified August 20 03:34 EDT 2017. Contains 290823 sequences.