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.

Previous Showing 11-15 of 15 results.

A274561 Numbers k such that sigma(k) == 0 (mod k+8).

Original entry on oeis.org

10, 49, 240, 550, 748, 1504, 3192, 7192, 7912, 10792, 17272, 30592, 979992, 1713592, 4526272, 8353792, 9928792, 11547352, 17999992, 89283592, 173482552, 361702144, 1081850752, 1845991216, 2146926592, 11097907192, 12985220152, 21818579968, 34357510144, 109170719992, 228354264064, 279632332792, 549746900992, 1511712719992, 2169800814592
Offset: 1

Views

Author

Paolo P. Lava, Jul 05 2016

Keywords

Examples

			sigma(10) mod (10 + 8) = 18 mod 18 = 0.

Crossrefs

Cf. A000203, A045770, A067702, A088833, A181598, A274551-A274560, A274562-A274566.

Programs

  • Mathematica
    Select[Range[10^6], Mod[DivisorSigma[1, #], # + 8] == 0 &] (* Michael De Vlieger, Jul 05 2016 *)

Extensions

a(16)-a(35) from Giovanni Resta

A274563 Numbers k such that sigma(k) == 0 (mod k+9).

Original entry on oeis.org

15, 208, 6976, 8415, 31815, 351351, 2077696, 20487159, 159030135, 536559616, 2586415095, 137433972736, 2199003332608
Offset: 1

Views

Author

Paolo P. Lava, Jul 06 2016

Keywords

Examples

			sigma(15) mod (15 + 9) = 24 mod 24 = 0.

Crossrefs

Cf. A045770, A067702, A088833, A181598, A223610, A274551-A274562, A274564-A274566.

Programs

  • Mathematica
    Select[Range[10^6], Mod[DivisorSigma[1, #], # + 9] == 0 &] (* Michael De Vlieger, Jul 06 2016 *)

Extensions

a(7)-a(13) from Giovanni Resta, Jul 06 2016

A274564 Numbers k such that sigma(k) == 0 (mod k-9).

Original entry on oeis.org

6, 7, 8, 10, 11, 15, 19, 24, 33, 105, 33705, 33624064, 2199041081344
Offset: 1

Views

Author

Paolo P. Lava, Jul 06 2016

Keywords

Examples

			sigma(10) mod (10 - 9) = 18 mod 1 = 0.

Crossrefs

Contains subsequence A223608.
Cf. A045770, A067702, A088833, A181598, A274551, A274552, A274553, A274554, A274556, A274557, A274558, A274559, A274560, A274561, A274562, A274563, A274565, A274566.

Programs

  • Magma
    [n: n in [10..2*10^6] | SumOfDivisors(n) mod (n-9) eq 0 ]; // Vincenzo Librandi, Jul 06 2016
  • Mathematica
    k = -9; Select[Range[Abs@k+1, 10^6], Mod[DivisorSigma[1, #], # + k] == 0 &] (* Vincenzo Librandi, Jul 06 2016 *)
  • PARI
    isok(k) = (k!=9) && (Mod(sigma(k), k-9) == 0); \\ Michel Marcus, May 30 2025

Extensions

a(12)-a(13) from Giovanni Resta, Jul 06 2016
Terms 6,7,8 inserted by Max Alekseyev, May 29 2025

A274559 Numbers k such that sigma(k) == 0 (mod k+7).

Original entry on oeis.org

8, 272, 7232, 30848, 516608, 134094848, 2146992128, 35184309174272
Offset: 1

Views

Author

Paolo P. Lava, Jul 05 2016

Keywords

Examples

			sigma(8) mod (8+7) = 15 mod 15 = 0.

Crossrefs

Contains subsequence A141546.
Cf. A045770, A067702, A088833, A181598, A274551, A274552, A274553, A274554, A274556, A274557, A274558, A274560, A274561, A274562, A274563, A274564, A274565, A274566.

Programs

  • Mathematica
    Select[Range[10^6], Mod[DivisorSigma[1, #], # + 7] == 0 &] (* Michael De Vlieger, Jul 05 2016 *)

Extensions

a(6)-a(7) from Giovanni Resta, Jul 05 2016
a(8) from Max Alekseyev, May 29 2025

A274565 Numbers k such that sigma(k) == 0 (mod k+10).

Original entry on oeis.org

14, 176, 1376, 3230, 3770, 6848, 114256, 125696, 544310, 561824, 740870, 2075648, 4199030, 4607296, 8436950, 33468416, 134045696, 199272950, 624032630, 1113445430, 1550860550, 85905593344, 2199001235456, 35184284008448
Offset: 1

Views

Author

Paolo P. Lava, Jul 06 2016

Keywords

Examples

			sigma(14) mod (14 + 10) = 24 mod 24 = 0.

Crossrefs

Contains subsequence A223611.
Contains 2 * odd terms of A223609.
Cf. A045770, A067702, A088833, A181598, A274551, A274552, A274553, A274554, A274556, A274557, A274558, A274559, A274560, A274561, A274562, A274563, A274564, A274566.

Programs

  • Magma
    [n: n in [1..2*10^6] | SumOfDivisors(n) mod (n+10) eq 0 ]; // Vincenzo Librandi, Jul 06 2016
  • Mathematica
    k = 10; Select[Range[Abs@k+1, 10^6], Mod[DivisorSigma[1, #], # + k] == 0 &] (* Vincenzo Librandi, Jul 06 2016 *)

Extensions

a(13)-a(23) from Giovanni Resta, Jul 06 2016
a(24) from Max Alekseyev, May 29 2025
Previous Showing 11-15 of 15 results.

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