login
A094447
Numbers which are the sum of two positive cubes and divisible by 13.
9
65, 91, 351, 468, 520, 559, 637, 728, 793, 1001, 1027, 1339, 1456, 1547, 1729, 1755, 2457, 2808, 3718, 3744, 3887, 4160, 4394, 4472, 4706, 4914, 4940, 5096, 5642, 5824, 6175, 6344, 7163, 7202, 7371, 7657, 8008, 8125, 8190, 8216, 9009
OFFSET
1,1
LINKS
EXAMPLE
Sums not divisible by 13 are shown in asterisks:
....|...1....8...27...64...125...216...343...512...729..1000..1331
------------------------------------------------------------------
1...|...*....*....*...65.....*.....*.....*.....*.....*..1001.....*
8...|...*....*....*....*.....*.....*...351...520.....*.....*..1339
27..|...*....*....*...91.....*.....*.....*.....*.....*..1027.....*
64..|..65....*...91....*.....*.....*.....*.....*...793.....*.....*
125.|...*....*....*....*.....*.....*...468...637.....*.....*..1456
216.|...*....*....*....*.....*.....*...559...728.....*.....*..1547
343.|...*..351....*....*...468...559.....*.....*.....*.....*.....*
512.|...*..520....*....*...637...728.....*.....*.....*.....*.....*
729.|...*....*....*..793.....*.....*.....*.....*.....*..1729.....*
1000|1001....*.1027....*.....*.....*.....*.....*..1729.....*.....*
1331|...*.1339....*....*..1456..1547.....*.....*.....*.....*.....*
MATHEMATICA
upto[n_] := Block[{t}, Union@ Reap[ Do[If[Mod[t = x^3 + y^3, 13] == 0, Sow@t], {x, n^(1/3)}, {y, Min[x, (n - x^3)^(1/3)]}]][[2, 1]]]; upto[10^4] (* Giovanni Resta, Jun 12 2020 *)
CROSSREFS
Sequence in context: A020140 A283656 A020194 * A020224 A063519 A299456
KEYWORD
nonn,easy
AUTHOR
Jun Mizuki (suzuki32(AT)sanken.osaka-u.ac.jp), Jun 09 2004
EXTENSIONS
Definition corrected by Robert Israel, Jun 12 2020
STATUS
approved