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

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

Offset

1,1

Comments

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

Links

Table of n, a(n) for n=1..14.

Example

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.

Mathematica

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

Crossrefs

Intersection of A353300 and A353301.

Cf. A001097, A004394, A068507, A321995.

Sequence in context: A028954 A035247 A321995 * A355159 A039885 A239197

Adjacent sequences: A353299 A353300 A353301 * A353303 A353304 A353305

Keyword

nonn,more

Author

Amiram Eldar, Apr 10 2022

Status

approved