cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A228556 Sums of two coprime positive cubes that are also sums of two coprime positive fifth powers.

Original entry on oeis.org

2, 32769, 14348908, 14381675, 1073741825, 1088090731, 30517578126, 30517610893, 30531927032, 31591319949, 43977108474, 470184984577, 500702562701, 4747561509944, 4747561542711, 4747575858850, 4748635251767, 4778079088068, 5217746494519
Offset: 1

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Author

Arkadiusz Wesolowski, Aug 25 2013

Keywords

Comments

Every term greater than 2 has at least one prime factor of the form 30*k + 1 and therefore is in A228541.

Examples

			14381675 is in the sequence since 32^3 + 243^3 = 8^5 + 27^5 = 14381675 and (32, 243) = (8, 27) = 1.

Links

Crossrefs

Cf. A035046, A202679, A228541, A228542.

Formula

A202679 INTERSECT A228542.

A374365 Numbers m such that abs(Sum_{k=1..m} [k|m]*A008683(k)*(-1)^(2*k/5)) = 0.

Original entry on oeis.org

11, 22, 31, 33, 41, 44, 55, 61, 62, 66, 71, 77, 82, 88, 93, 99, 101, 110, 121, 122, 123, 124, 131, 132, 142, 143, 151, 154, 155, 164, 165, 176, 181, 183, 186, 187, 191, 198, 202, 205, 209, 211, 213, 217, 220, 231, 241, 242, 244, 246, 248, 251, 253, 262, 264, 271
Offset: 1

Views

Author

Mats Granvik, Jul 06 2024

Keywords

Comments

Conjecture: Numbers having a prime factor congruent to 1 mod 10.

Crossrefs

Cf. A008683, A009003, A050931, A228541.

Programs

  • Mathematica
    nn = 274; Flatten[Position[ParallelTable[Abs[Sum[If[Mod[n, k] == 0, 1, 0]*((-1)^( 2*k/5))*MoebiusMu[k], {k, 1, n}]], {n, 1, nn}], 0]]
Showing 1-2 of 2 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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