A094447 Numbers which are the sum of two positive cubes and divisible by 13.

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

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

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

Adjacent sequences: A094444 A094445 A094446 * A094448 A094449 A094450

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