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 A130555 Numbers that are sums of sixth powers of two distinct primes. 6
 793, 15689, 16354, 117713, 118378, 133274, 1771625, 1772290, 1787186, 1889210, 4826873, 4827538, 4842434, 4944458, 6598370, 24137633, 24138298, 24153194, 24255218, 25909130, 28964378, 47045945, 47046610, 47061506, 47163530 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS This is to 6th powers as A130292 is to fifth powers, A130873 is to 4th powers and A120398 is to cubes. These can never be prime, as sixth powers are cubes and the sum of cubes factorizations applies. There are semiprimes for values beginning a(1) = 793, a(2) = 15689 = 29 * 541, a(4) = 117713 = 53 * 2221, a(11) = 4826873 = 173 * 27901. LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..8000 FORMULA {A001014(A000040(i)) + A001014(A000040(j)) for i > j}. EXAMPLE a(1) = prime(1)^6 + prime(2)^6 = 2^6 + 3^6 = 64 + 729 = 793 = 13 * 61. MATHEMATICA Select[Sort[Flatten[Table[Prime[n]^6 + Prime[k]^6, {n, 15}, {k, n - 1}]]], # <= Prime[15^6] &] Union[Total/@Subsets[Prime[Range[20]]^6, {2}]] (* Harvey P. Dale, Mar 11 2012 *) CROSSREFS Cf. A000040, A001014, A050997, A120398, A122616, A130873. Sequence in context: A045246 A095812 A212239 * A133537 A213471 A075667 Adjacent sequences:  A130552 A130553 A130554 * A130556 A130557 A130558 KEYWORD easy,nonn AUTHOR Jonathan Vos Post, Aug 09 2007 STATUS approved

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Last modified November 29 07:48 EST 2021. Contains 349416 sequences. (Running on oeis4.)