A102658 Numbers which are the sum of two positive cubes and divisible by 31.

217, 341, 1395, 1674, 1736, 2728, 4123, 5425, 5642, 5859, 6293, 7471, 7657, 8029, 8587, 9207, 9269, 9331, 10261, 11160, 11377, 12679, 12896, 13392, 13888, 14167, 14911, 15841, 16120, 17577, 17701, 19747, 20026, 21824, 21979, 24149, 24397

Offset: 1

Author

Jun Mizuki (suzuki32(AT)sanken.osaka-u.ac.jp), Feb 02 2005

Keywords

• nonn
• easy

Links

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

Crossrefs

Cf. A003325, A101421 (divisible by k=7), A101852 (k=11), A094447 (k=13), A099178 (k=17), A102619 (k=19), A101806 (k=23), A224483 (k=29), A102618 (k=37).

Programs

Mathematica

upto[n_] := Block[{t}, Union@ Reap[ Do[If[Mod[t = x^3 + y^3, 31] == 0, Sow@t], {x, n^(1/3)}, {y, Min[x, (n - x^3)^(1/3)]}]][[2, 1]]]; upto[24500] (* Giovanni Resta, Jun 12 2020 *)