login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A113490
Semiprimes a such that there exist three semiprimes b, c and d with a^3=b^3+c^3+d^3.
2
206, 519, 703, 869, 1418, 1923, 1945, 2066, 2095, 2127, 2446, 2759, 2867, 2881, 2901, 2913, 2974, 3099, 3155, 3207, 3383, 3398, 3545, 3649, 3777, 3814, 3898, 4435, 4766, 4778, 4873, 4963, 5091, 5105, 5165, 5534, 5582, 5638, 5771, 5834, 5855, 6033, 6098
OFFSET
1,1
COMMENTS
This is the semiprime analog of A114923.
There are only two such semiprimes < 10^4 with more than one solution: 2095 and 9897.
EXAMPLE
206^3 = 35^3 + 77^3 + 202^3.
519^3 = 4^3 + 303^3 + 482^3
703^3 = 111^3 + 291^3 + 685^3.
869^3 = 466^3 + 629^3 + 674^3.
2095^3 = 339^3 + 753^3 + 2059^3 = 543^3 + 1119^3 + 1969^3 (two ways).
9897^3 = 537^3 + 1454^3 + 9886^3 = 2071^3 + 3183^3 + 9755^3 (two ways).
Each of these numbers (other than the exponent 3) is a semiprime (A001358).
CROSSREFS
Sequence in context: A252270 A113934 A260101 * A054007 A285754 A201032
KEYWORD
nonn
AUTHOR
Jonathan Vos Post, Jan 09 2006
EXTENSIONS
Extended by Ray Chandler, Jan 20 2006
STATUS
approved