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 A225909 Numbers that are both a sum of two positive cubes and a difference of two consecutive cubes. 3
 91, 217, 1027, 4921, 8587, 14911, 31519, 39331, 106597, 117019, 136747, 185257, 195841, 265519, 281827, 616987, 636181, 684019, 712969, 724717, 736561, 955981, 1200169, 1352737, 1405621, 1771777, 2481571, 2756167, 2937331, 4251871, 4996171, 5262901 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Solutions x to the equations x = a^3 + b^3 = (c+1)^3 - c^3 in positive integers. The values of c are A226902. The intersection of A003325 and A003215. Subsequence of A225908 = numbers that are both a sum and a difference of two positive cubes. Shiraishi's solution to Gokai Ampon's equation u^3 + v^3 + w^3 = n^3 (see A023042 and A226903) shows that the sequence is infinite. REFERENCES Shiraishi Chochu (aka Shiraishi Nagatada), Shamei Sampu (Sacred Mathematics), 1826. LINKS Chai Wah Wu, Table of n, a(n) for n = 1..5000 David Eugene Smith and Yoshio Mikami, A History of Japanese Mathematics, Open Court, Chicago, 1914; Dover reprint, 2004; pp. 233-235. Wikipedia (French), Shiraishi Nagatada Wikipedia (German), Shiraishi Nagatada FORMULA a(n) = (A226902(n)+1)^3 - A226902(n)^3. EXAMPLE 3^3 + 4^3 = 6^3 - 5^3 = 91, so 91 is a member. MATHEMATICA Select[#[]-#[]&/@Partition[Range^3, 2, 1], Count[ IntegerPartitions[ #, {2}], _?(AllTrue[Surd[#, 3], IntegerQ]&)]>0&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Sep 07 2018 *) CROSSREFS Cf. A003215, A003325, A023042, A181123, A225908, A226902, A226903. Sequence in context: A260064 A207077 A293648 * A051973 A290812 A000864 Adjacent sequences:  A225906 A225907 A225908 * A225910 A225911 A225912 KEYWORD nonn AUTHOR Jonathan Sondow, Jun 21 2013 STATUS approved

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Last modified April 4 08:58 EDT 2020. Contains 333213 sequences. (Running on oeis4.)