A353301 -id:A353301 - 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

A353302 Numbers k such that A004394(k)-1 and A004394(k)+1 are twin primes.

Original entry on oeis.org

3, 4, 5, 9, 11, 12, 24, 25, 76, 82, 105, 139, 217, 1370

Offset: 1

Amiram Eldar, Apr 10 2022

a(15) > 10^5, if it exists.

			3 is a term since the third superabundant number is A004394(3) = 4 and {4-1, 4+1} = {3, 5} is a twin primes pair.

Intersection of A353300 and A353301.

Cf. A001097, A004394, A068507, A321995.

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

cp's OEIS Frontend

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

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