A353302 -id:A353302 - cp's OEIS frontend

A353300 Numbers k such that A004394(k)-1 is prime.

3, 4, 5, 6, 8, 9, 11, 12, 13, 14, 15, 16, 19, 20, 24, 25, 26, 30, 32, 41, 47, 48, 49, 51, 57, 59, 76, 82, 83, 92, 104, 105, 117, 119, 131, 134, 137, 139, 143, 154, 166, 170, 172, 180, 209, 214, 215, 216, 217, 227, 231, 234, 247, 265, 269, 271, 284, 317, 327, 348

Offset: 1

Amiram Eldar, Apr 10 2022

nonn

First differs from A306588 at n=15.

			3 is a term since A004394(3)-1 = 4-1 = 3 is prime.

Amiram Eldar, Table of n, a(n) for n = 1..314

Cf. A004394, A072826, A306588, A353301, A353302.

s = {}; abm = 0; k = 0; Do[ab = DivisorSigma[-1, n]; If[ab > abm, abm = ab; k++; If[PrimeQ[n - 1], AppendTo[s, k]]], {n, 1, 10^6}]; s

A353301 Numbers k such that A004394(k)+1 is prime.

Original entry on oeis.org

1, 2, 3, 4, 5, 7, 9, 11, 12, 18, 21, 24, 25, 28, 35, 45, 46, 50, 56, 70, 73, 76, 78, 79, 82, 89, 94, 105, 113, 116, 118, 121, 123, 124, 138, 139, 153, 157, 159, 164, 197, 201, 203, 210, 217, 253, 261, 273, 280, 283, 287, 342, 352, 356, 381, 396, 437, 450, 471

Offset: 1

Amiram Eldar, Apr 10 2022

nonn

First differs from A306587 at n=11.

			1 is a term since A004394(1)+1 = 1+1 = 2 is prime.

Amiram Eldar, Table of n, a(n) for n = 1..300

Cf. A004394, A072828, A306587, A353300, A353302.

s = {}; abm = 0; k = 0; Do[ab = DivisorSigma[-1, n]; If[ab > abm, abm = ab; k++; If[PrimeQ[n + 1], AppendTo[s, k]]], {n, 1, 10^6}]; s

A375198 Numbers k such that A025487(k)-1 and A025487(k)+1 are twin primes.

Original entry on oeis.org

3, 4, 6, 9, 13, 15, 20, 21, 24, 29, 30, 42, 54, 56, 59, 72, 77, 83, 96, 104, 105, 109, 138, 161, 166, 174, 186, 203, 208, 221, 232, 237, 266, 270, 288, 295, 336, 338, 347, 387, 389, 395, 400, 401, 449, 468, 469, 472, 479, 506, 520, 543, 584, 617, 633, 643, 668

Offset: 1

Amiram Eldar, Aug 04 2024

nonn

Amiram Eldar, Table of n, a(n) for n = 1..10000

Cf. A001097, A001359, A006512, A014574, A025487, A375197.

Similar sequences: A321995, A353302.

Position[Cases[Import["https://oeis.org/A025487/b025487.txt", "Table"], {, }][[;; , 2]], _?(PrimeQ[# - 1] && PrimeQ[# + 1] &)] // Flatten

A025487(a(n)) = A375197(n).

cp's OEIS Frontend

A353300 Numbers k such that A004394(k)-1 is prime.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Programs

Mathematica

A353301 Numbers k such that A004394(k)+1 is prime.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Programs

Mathematica

A375198 Numbers k such that A025487(k)-1 and A025487(k)+1 are twin primes.

Views

Author

Keywords

Links

Crossrefs

Programs

Mathematica

Formula